bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulation of MAPK-phosphatase 1 gene expression by glucocorticoids occurs through a tethering mechanism involving C/EBP
Authors: Johansson-Haque Krishan , Palanichamy Elanchelian , Okret Sam
Published: August 2008

Glucocorticoids (GCs) are known to inhibit mitogen-activated protein kinase (MAPK) signaling. This has been suggested to involve induced expression of MAPK-phosphatase 1 (DUSP1), which dephosphorylates and inactivates MAPKs. However, the mechanism for the transcriptional activation by GCs of DUSP1 or the identification of a GC-responsive region of the gene has so far not been described. To identify GC receptor (GR) binding to the human DUSP1 promoter in vivo, we used a chromatin immunoprecipitation (ChIP) assay and found GR to bind to a region ∼ −1.4 kb upstream of the transcription start site. Using promoter deletion constructs, we identified a GC-responsive region between position −1266 and −1380 bp of the DUSP1 promoter. However, no direct binding of GR to this GC-responsive region was detected in an electrophoretic mobility shift assay (EMSA). Instead, we identified binding of CCAAT/enhancer-binding protein beta (C/EBPβ) to a region between −1311 and −1304 bp of the DUSP1 promoter by EMSA and ChIP. Furthermore, mutation of the C/EBP binding site resulted in a dramatic loss of GC-inducible reporter gene expression, demonstrating the GC responsiveness of the DUSP1 gene to be located to a binding site for C/EBP in the DUSP1 promoter. Also, given that a GR mutant (GRLS7), incapable of transactivating through GC-responsive elements, still was able to bind to the DUSP1 gene in vivo and induce DUSP1 mRNA expression following treatment with GCs suggests the mode of GC activation to be mediated by a tethering mechanism involving the GR and the DUSP1 promoter-bound C/EBPβ.
Epithelial injury induces an innate repair mechanism linked to cellular senescence and fibrosis involving IGF-binding protein-5
Authors: Allan Gordon J , Beattie James , Flint David J
Published: August 2008

Fibrosis is associated with epithelial repair. It involves the activation of fibroblasts, increased production of extracellular matrix proteins and transdifferentiation to contractile, myofibroblasts that aid in wound contraction. This provisional matrix plugs the injured epithelium and provides a scaffold for epithelial cell migration, involving an epithelial–mesenchymal transition (EMT). When epithelial injury involves blood loss, this leads to platelet activation, the production of several growth factors and an acute inflammatory response. Under normal circumstances, the epithelial barrier is repaired and the inflammatory response resolves. However, in fibrotic disease, the fibroblast response continues, resulting in unresolved wound healing. The fibrotic diseases range from scleroderma, where the problem may be restricted to the skin and where it is not life-threatening, through to systemic forms that can manifest as, for example, idiopathic pulmonary fibrosis, in which death is inevitable within 3–5 years. Anti-inflammatory treatments have failed to ameliorate the disease condition and focus has instead turned to transforming growth factor-β1 (TGFB1), since it induces many of the processes involved, including fibroblast activation and EMT. Most recently, however, a new player in this process has been described, IGF-binding protein-5 (IGFBP5). IGFBP5 has also been shown to induce similar effects to TGFB1, but, in addition, it is strongly implicated in the process of senescence which is now believed to be a significant factor in these diseases. We examine the evidence for this role of IGFBP5 and identify some of the therapeutic targets which might be used to ameliorate these diseases of unknown cause.
XANES Speciation of Phosphorus in Organically Amended and Fertilized Vertisol and Mollisol
Authors: Ajiboye Babasola , Akinremi Olalekan O. , Hu Yongfeng , Jürgensen Astrid
Published: August 2008

Knowledge of the dominant P species present in the soil following the application of organic amendments and fertilizer is important in understanding the fate of P in the environment. This study was performed to identify P species in two calcareous soils, an Osborne series (Typic Humicryert) and a Lakeland series (Typic Calciudoll), treated with organic amendments (biosolids and hog and dairy cattle manure) and fertilizer (monoammonium phosphate, MAP). Phosphorus 1s x‐ray absorption near‐edge structure (XANES) spectroscopy was used to speciate P compounds in these amended soils. The result showed that “adsorbed P” was the dominant P species in both soils. For the Osborne soil, the unamended soil (control) and those amended with biosolids and MAP contained an appreciable amount of hydroxyapatite (HAP), the most thermodynamically favored Ca phosphate. In addition, soils amended with biosolids or hog or dairy manures contain β‐tricalcium phosphate (TRICAL), a more soluble form of Ca phosphate than HAP. The amended Lakeland soils contained a variety of species in addition to the dominant “adsorbed P.” While TRICAL was found in all the amended soils except in that amended with hog manure, HAP was present in appreciable amount only in the unamended soil. Overall, the adsorbed P, most likely through inner‐sphere complexation, in these amended soils may not be readily available as a source of P into the environment. In addition, the HAP and TRICAL will have limited solubility, and thus, are probably only a very minor source of P in the environment.
Phosphate Mobilization by Citric, Tartaric, and Oxalic Acids in a Clay Loam Ultisol
Authors: Wang Y. , He Y. , Zhang H. , Schroder J. , Li C. , Zhou D.
Published: August 2008

Phosphate mobilization by organic acids has been shown to be soil type dependent and controlled by the soil's intrinsic P status. The objective of this study was to evaluate the capacity and mechanisms of three organic acids in the mobilization of phosphate from an upland clay loam Ultisol that had received different long‐term fertilizer treatments. Soil samples were incubated at 25 ± 1°C and 40% moisture content for 3 wk with citric, tartaric, or oxalic acid at 1.0 mmol kg−1 of soil. Soil pH, inorganic P fractions, and plant‐available P (Olsen P) were analyzed after incubation. The results indicated that Olsen P and the loosely bound P extracted with 1.0 mol L−1 NH4Cl (NH4Cl‐P) were significantly increased by the treatment of the three organic acids, and Fe phosphate (Fe‐P), occluded phosphate (Oc‐P), and Ca phosphate (Ca‐P) were mobilized and released to various degrees as well. The order of increased mobilization of P by the organic acids was citric acid > tartaric acid > oxalic acid. These three organic acids have the potential to increase the availability of P in soil but need to be evaluated at the field scale.
Nondestructive System for Analyzing Carbon in the Soil
Authors: Wielopolski Lucian , Hendrey George , Johnsen Kurt H. , Mitra Sudeep , Prior Stephen A. , Rogers Hugo H. , Torbert H. Allen
Published: August 2008

Carbon is an essential component of life and, in its organic form, plays a pivotal role in the soil's fertility, productivity, and water retention. It is an integral part of the atmospheric–terrestrial C exchange cycle mediated via photosynthesis; furthermore, it emerged recently as a new trading commodity, i.e., “carbon credits.” When carefully manipulated, C sequestration by the soil could balance and mitigate anthropogenic CO2 emissions into the atmosphere that are believed to contribute to global warming. The pressing need for assessing the soil's C stocks at local, regional, and global scales, now in the forefront of much research, is considerably hindered by the problems besetting dry‐combustion chemical analyses, even with state‐of‐the‐art procedures. To overcome these issues, we developed a new method based on gamma‐ray spectroscopy induced by inelastic neutron scattering (INS). The INS method is an in situ, nondestructive, multielemental technique that can be used in stationary or continuous‐scanning modes of operation. The results from data acquired from an investigated soil mass of a few hundred kilograms to an approximate depth of 30 cm are reported immediately. Our initial experiments have demonstrated the feasibility of our proposed approach; we obtained a linear response with C concentration and a detection limit between 0.5 and 1% C by weight.
Respiration in Boreal Forest Soil as Determined from Carbon Dioxide Concentration Profile
Authors: Pumpanen Jukka , Ilvesniemi Hannu , Kulmala Liisa , Siivola Erkki , Laakso Heikki , Kolari Pasi , Helenelund Christer , Laakso Mikko , Uusimaa Maria , Hari Pertti
Published: August 2008

Soil respiration forms a substantial part of the ecosystem respiration. However, the respiration measurements conducted with chambers on the soil surface do not give information on the vertical distribution of CO2 sources and its seasonal dynamics. We used permanently installed CO2 probes to determine the CO2 profile in a boreal coniferous forest soil and calculated the CO2 efflux from the concentration profile with a dynamic model. There was an increase in both soil CO2 efflux and soil air CO2 concentration over the 2.5‐mo study period between April 15 and June 30. The CO2 efflux determined from the concentration profile was in relatively good agreement with the CO2 efflux measured by open dynamic chamber method. We also determined the respiration of different soil horizons and estimated the contribution of recent photosynthate to total respiration. Humus layer and A‐horizon contributed 69.9%, B‐horizon 19.8%, and C‐horizon 10.4% of the total CO2 efflux. The Q10 values determined over 7‐d periods were on average 2.54, 3.66, and 13.14 in A‐, B‐, and C‐horizons, respectively. However, when fitted over the whole 2.5‐mo time period, the Q10 values were 3.56, 5.57, and 17.45 in A‐, B‐, and C‐horizons, respectively. Based on the different temperature responses obtained over 7‐d and 2.5‐mo time periods, we estimated the contribution of recent photosynthate to soil respiration. In April, the respiration originating from recent photosynthate contributed about 2% of the total respiration in the A‐, B‐, and C‐horizons and increased to 32, 35, and 24% by June 30 in the respective soil horizons.
A Test of Coupled Soil Heat and Water Transfer Prediction under Transient Boundary Temperatures
Authors: Heitman J. L. , Horton R. , Ren T. , Nassar I. N. , Davis D. D.
Published: August 2008

Diffusion‐based coupled soil heat and water transfer theory includes capability to describe transient behavior. Unfortunately, laboratory tests of theory typically include a single initial water content distribution with a single set of boundary conditions, rather than providing a set of experimental conditions with a range of measurements for comparison with predictions. Agreement between theory and measurements can result from calibration, but this provides an incomplete test of theory. The objective of this work was to test diffusion‐based coupled heat and water transfer theory by comparing theory‐based predictions with measured transient temperature and water content distributions. Data from a single boundary condition were used for calibration of each of two soils, silt loam and sand. Subsequent testing was performed at additional boundary and initial conditions using measurements from the same soil. Results indicate that the theory can be calibrated for a single boundary condition with adjustment of soil saturated hydraulic conductivity and/or the vapor enhancement factor, which adjust the liquid and vapor fluxes, respectively. For silt loam, calibration reduced Root Mean Square Error (RMSE) by 67 and 18% for water content and temperature distributions, respectively. For sand, RMSE was reduced by 14 and 46% for water content and temperature, respectively. Using this calibration, there was agreement between calculated and measured distributions for additional boundary and initial conditions with RMSE ≤ 0.03 m3m−3 and 1.28°C for water content and temperature distributions, respectively. However, when the boundary temperature gradient was instantly reversed, noticeable differences occurred between measured and calculated patterns of heat and moisture redistribution. The theory described observations well when boundary temperature conditions were changed gradually, but results suggested a need for further development of coupled heat and water transfer theory combined with testing under transient conditions to make improvements in the description of transfer mechanisms.
Analytical Solution of Heat Pulse Method in a Parallelepiped Sample Space with Inclined Needles
Authors: Liu Gang , Li Baoguo , Ren Tusheng , Horton Robert , Si Bing C.
Published: August 2008

The heat pulse method enables estimation of soil thermal diffusivity (k), volumetric heat capacity (C), thermal conductivity, and water content. The heater needle and temperature‐sensing needle may deflect during probe insertion into soils. The impact of needle deflection on estimates of C and k has not been fully studied theoretically or experimentally. We defined θ to be the polar angle of needle deviation from the z axis and φ to be the azimuthal angle in the x–y plane. Transient‐state analytical solutions were derived for an inclined and pulsed finite line source in a parallelepiped sample with zero surface temperature and adiabatic boundary conditions. For a heat pulse sensor with 6‐mm needle spacing and a heater needle of 4‐cm length in a given parallelepiped (5 by 5 by 5 cm, assumed to be filled with air‐dry sand), model errors in C and k were about −11.3 and 12.1%, respectively, for an inclined heater needle with θ = 1° and φ = 0°. Model errors in C and k were about −11.2 and 12.1%, respectively, for an inclined sensor needle with θ = 1° and φ = 180°. When −6 ≤ θ ≤ 6° for either the heater or the sensor needle, the temperature curves could be approximated rather well by a pulsed infinite line source model with a modified probe spacing that accounted for the inclination. For various heating durations and strengths, the errors in both k and C were relatively constant when all other parameters were fixed; however, the errors in both C and k decreased monotonically and slowly as k increased. The model errors in C and k were similar for four soil conditions with different thermal properties in the range −6 ≤ θ ≤ 2°.
Denitrification and Nitrate Consumption in an Herbaceous Riparian Area and Perennial Ryegrass Seed Cropping System
Authors: Davis Jennifer H. , Griffith Stephen M. , Horwath William R. , Steiner Jeffrey J. , Myrold David D.
Published: August 2008

Riparian ecosystems have the capacity to lower NO3−concentrations in groundwater entering from nonpoint agricultural sources. The processes responsible for decreases in riparian groundwater NO3−concentrations in the Willamette Valley of Oregon are not well understood. Our objective was to determine if denitrification and/or dissimilatory NO3−reduction to NH4+(DNRA) could explain decreases in groundwater NO3−moving from a perennial ryegrass cropping system into a mixed‐herbaceous riparian area. In situ denitrification rates (DN) were not different between the riparian area (near‐stream or near‐cropping system) and cropping system the first year. In the second year, during the transition to a clover planting, DN was highest just inside of the riparian/cropping system border. Median denitrification enzyme activity (DEA) rates ranged from 29.5 to 44.6 mg N2O‐N kg−1d−1for surface soils (0–15 cm) and 0.7 to 1.7 μg N2O‐N kg−1d−1in the subsoil (135–150 cm). Denitrification enzyme activity rates were not different among the zones and were most often correlated to soil moisture and NH4+Nitrate additions to surface soils increased DEA rates, indicating a potential to denitrify additional NO3−Based on groundwater velocity estimates, NO3−(3.8 mg NO3−‐N L−1) entering the riparian surface soil could have been consumed in 0.2 to 7 m by denitrification and 0.03 to 1.0 m by DNRA. Denitrification rates measured in the subsoil could not explain the spatial decrease in NO3−However, with the potentially slow movement of water in the subsoil, denitrification and DNRA (0 to 264 μg N kg−1d−1) together could have completely consumed NO3−within 0.5 m of entering the riparian zone.
Using Support Vector Machines to Develop Pedotransfer Functions for Water Retention of Soils in Poland
Authors: Lamorski K. , Pachepsky Y. , Sławiński C. , Walczak R. T.
Published: August 2008

Pedotransfer functions (PTFs), which estimate soil hydraulic parameters from easy to measure soil properties, are an important data source for hydrologic modeling. Recently artificial neural networks (ANNs) have become the tool of choice in PTF development. Recent developments in machine learning methods include the growing research and application of the alternative data‐driven method called Support Vector Machines (SVMs). Support Vector Machines have gained popularity in many traditionally ANN dominated fields. Using the SVM eliminates the local minimum issue—the minimum found is always the global one. The objective of this work was to see whethers using the SVM to develop PTFs may have some advantages compared with the ANN. We have used the Soil Profiles Bank of Polish Mineral Soils that includes hydraulic properties for 806 soil samples taken from 290 soil profiles. This database was repeatedly randomly split into training and testing data sets, and both SVMs and ANNs were trained and tested for each split with bulk density, sand and clay as input variables, and water contents at 11 soil water potentials as the output variables. The PTF performance was evaluated by using the test datasets to compute the coefficient of determination, the root‐mean‐squared error, and the slope and the intercept of the linear regression “predicted vs. measured water contents.” The three‐parameter SVMs performed mostly better than or with the same accuracy as the eleven‐parameter ANNs. The advantage of SVM was more pronounced at soil matric potentials where larger relative errors have been encountered and the correlation between predicted and measured soil water contents was lower. It is worthwhile to consider SVM as a tool to develop PTF.
Thermal Neutron Computed Tomography of Soil Water and Plant Roots
Authors: Tumlinson Leanne G. , Liu Hungyuan , Silk Wendy K. , Hopmans Jan W.
Published: August 2008

Neutron radiography is a noninvasive imaging technique that measures the attenuation of thermal neutrons, as is done with x‐ray and γ‐ray radiography, to characterize the internal composition of materials. Neutron and x‐ray imaging are complementary techniques, with neutron imaging especially well suited for materials containing H atoms and other low‐atomic‐weight attenuating materials. Although neutron computed tomography (NCT) techniques are routinely used in engineering, relatively little is known about their application to soils. We developed new techniques that use thermal neutron attenuation to measure the spatial and temporal distribution of water in soils and near roots at near 0.5‐mm spatial resolution or higher. The neutron source was a Mark II Triga Reactor at McClellan Nuclear Radiation Center in Sacramento, CA. After calibration using both deuterated and regular water, the effects of beam hardening and neutron scattering could be corrected for, provided that the total path length for a soil–water mixture does not exceed 1.0 cm, limiting soil sample thickness to about 2.5 cm. Using regular water, for a wide range of soil water content values, experiments demonstrated that NCT is sensitive to small changes in soil volumetric water content, allowing estimation of the spatial distribution of soil water, roots, and root water uptake. Although the spatial resolution of the applied NCT system was 80 μm, an error analysis showed that the averaging measurement volume should be not less than about 0.5 mm for the uncertainty in volumetric water content to be minimized to near 0.01 m3 m−3 A single root water uptake experiment with a corn (Zea mays L.) seedling demonstrated the successful application of NCT, with images showing spatially variable soil water content gradients in the rhizosphere and bulk soil.
Capillary Electrophoresis and Fluorescence Excitation‐Emission Matrix Spectroscopy for Characterization of Humic Substances
Authors: He Zhongqi , Ohno Tsutomu , Wu Fengchang , Olk Daniel C. , Honeycutt C. Wayne , Olanya Modesto
Published: August 2008

Capillary electrophoresis (CE) and fluorescence spectroscopy have been used in natural organic matter (NOM) studies. In this study, we characterized five fulvic acids (FAs), six humic acids (HAs), and two unprocessed NOM samples obtained from the International Humic Substances Society (IHSS) using these two analytical methods. The electropherograms of all samples revealed three peak features. The first and third peaks were sharp. The second peak had a broad, hump‐shaped feature. The pattern and shapes of these peaks were different among the FA, HA, and unprocessed NOM samples. Excitation‐emission matrix (EEM) fluorescence spectroscopic analysis revealed that each of the 13 investigated samples contained four components. However, the relative amounts of the four components varied with sample origin. Autoclaving these samples for 1 h (heat decomposition) produced additional CE peaks and changed portions of the four fluorophore components, indicating that both methods can be used to investigate the dynamics of NOM decomposition. Although four fluorophore components were present in each of the three CE fractions, their relative abundances varied among the three CE fractions. Specifically, Fraction 1 and 2 were rich in Component 1 and 4, but sparse in Component 2, compared with their original samples. Fraction 2 also contained less Component 3. The distribution of the four components in Fraction 3 was similar to that of the original samples. The mutual relevance of data collected from each of the two methods provided novel insight into the correlation of complex NOM fluorescence spectra to specific NOM fractions.
Cotton Nitrogen Management in a High‐Residue Conservation System: Cover Crop Fertilization
Authors: Reiter M. S. , Reeves D. W. , Burmester C. H. , Torbert H. A.
Published: August 2008

Nitrogen is required for adequate residue production from cereal cover crops used in no‐till cotton (Gossypium hirsutum L.) production, but residues can immobilize N needed by cotton. We conducted a 3‐yr field study on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudult) in northern Alabama to test N fertilizer practices for cotton grown with a rye (Secale cereale L.) cover crop and conservation tillage. Nitrogen rates applied to the rye cover crop were 0, 34, and 67 kg N ha−1 and cotton N rates were 0, 45, 90, and 135 kg N ha−1 Additionally, 15N microplots were established in cover crop N treatments of 34 kg N ha−1 and in cotton treatments of 90 kg N ha−1 Data collected included cover crop aerial biomass, cover crop C/N ratios, cotton leaf N at first flower, lint yield, lint quality, and 15N in plant and soil samples. Cotton grown in unfertilized rye treatments needed 57 to 60% (38–40 kg N ha−1) more N to maximize yields above median conventional tillage N recommendations (67 kg N ha−1). Cover crop N rates of 67 kg N ha−1 maximized cover crop biomass production for soil protection and soil organic matter aggradation. If the cover crop was fertilized, minimum cotton N applications of 70 and 76 kg N ha−1 were needed for economic optimum and maximum lint yield, respectively. We speculate that cotton N rates may be decreased in the future as new N and C pool equilibria are reached.
Cotton Nitrogen Management in a High‐Residue Conservation System: Source, Rate, Method, and Timing
Authors: Reiter M. S. , Reeves D. W. , Burmester C. H.
Published: August 2008

More than 70% of cotton (Gossypium hirsutum L.) grown in the Tennessee Valley of northern Alabama is produced using conservation tillage systems with cereal cover crops. The resulting decreased N efficiency requires development of new N fertilizer recommendations. We conducted a replicated 3‐yr field study on a Decatur silt loam (fine, kaolinitic, thermic Rhodic Paleudult) to determine the effects of N source (NHNO3 [AN] and urea–NH4NO3 [320 g N kg−1, UAN]), N rates (0, 45, 90, 135, and 180 kg N ha−1), N application timing (all at‐planting or 50:50 split between planting and first match head square), and N application method (banded or broadcast) on cotton grown in high‐residue rye (Secale cereale L.) conservation systems. Generally, 67 to 80% more N was needed than average conventional N rate recommendations to reach optimal yields if N was split applied, while N applied at‐planting had yield responses with 169% of the recommended N rate. Urea–NH4NO3 applications resulted in greater yields when banded at‐planting (1045 kg lint ha−1), while AN was more effective when broadcast applied at‐planting or in split applications (1002 and 996 kg lint ha−1, respectively). Chlorophyll meter readings, petiole NO3, and leaf N were not useful predictors of cotton N deficiency or yield. The most efficient practice is to apply 88% more N (126 kg N ha−1 total) than the mean conventional N cotton recommendation as a broadcast split application using AN. We speculate that N requirements may be decreased with time as C and N pools reach a new equilibrium.
Equivalent Parallel and Perpendicular Unsaturated Hydraulic Conductivities: Arithmetic Mean or Harmonic Mean?
Authors: Zhu Jianting
Published: August 2008

For saturated flows, it is well known that the equivalent parallel hydraulic conductivity is equal to the arithmetic mean of all individual hydraulic conductivities of the layers parallel to flows, and the equivalent perpendicular hydraulic conductivity is equal to the harmonic mean of all individual hydraulic conductivities of the layers perpendicular to flows. Due to the nonlinear relationship between the unsaturated hydraulic conductivity and the saturation, the validity of the same schemes for unsaturated flows needs to be examined. This study investigated equivalent hydraulic conductivities for unsaturated vertical flows under two distinct soil layering scenarios, layers parallel to flows (i.e., parallel vertical slabs or columns) and layers perpendicular to flows (i.e., horizontal layers). The two scenarios are referred to as the horizontal heterogeneity scenario and vertical heterogeneity scenario, respectively. The main objectives of this study were to: (i) examine the appropriateness of using simple arithmetic and harmonic means of hydraulic conductivity for unsaturated flows for the horizontal and vertical heterogeneity scenarios; and (ii) investigate the equivalent unsaturated hydraulic conductivities that are applicable to large‐scale hydrologic process modeling. The considered domain is typical for unsaturated flow that lies between the ground surface at the top and the groundwater table at the bottom. Results demonstrate that the arithmetic mean for the horizontal heterogeneity scenario and the harmonic mean for the vertical heterogeneity scenario, extended from the saturated flow situations, would introduce large relative errors in simulating the actual flux for coarser textured soils and for heterogeneous soils with large hydraulic parameter variances.
Cation Exchange Capacity and Composition of Soluble Soil Organic Matter Fractions
Authors: Kaiser M. , Ellerbrock R. H. , Gerke H. H.
Published: August 2008

The cation exchange capacity (CEC) of soils depends on the amount and composition not only of clay minerals but also of soil organic matter (SOM). While the CEC of soil clay minerals has been intensively studied, little is known about the CEC of organic matter (OM) fractions, in particular those obtained with newly developed SOM extraction techniques. The objective of this study was to develop and test a method to quantitatively determine the CEC of extracted OM fractions and to relate CEC(OM) to OM functional groups possibly responsible for sorption of cations. Water‐ and pyrophosphate‐soluble OM fractions were sequentially extracted from differently managed arable soils of two well‐known long‐term field experiments. The CEC of a freeze‐dried pyrophosphate‐soluble OM fraction [OM(PY)] (0.03 g) mixed with quartz sand (4.97 g) was determined by applying the standard percolation method. The chemical composition of OM(PY) was analyzed by Fourier‐transform infrared (FTIR) spectroscopy. For all plots except those fertilized with farmyard manure, the sorption properties of the OM(PY) fraction were found to be site specific and to reflect soil and crop rotation effects. The relative contribution of the CEC of OM(PY) to the CEC of the soil (0.8–11.6%) is dependent on soil C content and extractability. For all plots, however, the relative contents of carboxylic functional groups in OM(PY) determined with FTIR spectroscopy was found to be linearly related to the CEC of the OM(PY), similar to pure organic substances. This relationship indicates the usefulness of CEC determination on OM(PY) fractions. The results suggest that the relative contents of carboxylic functional groups in OM(PY) reflect long‐term effects of fertilization and crop rotation on the sorption properties of the SOM.
Full‐Inversion Tillage and Organic Carbon Distribution in Soil Profiles: A Meta‐Analysis
Authors: Angers D. A. , Eriksen-Hamel N. S.
Published: August 2008

While the adoption of no‐till (NT) usually leads to the accumulation of soil organic C (SOC) in the surface soil layers, a number of studies have shown that this effect is sometimes partly or completely offset by greater SOC content near the bottom of the plow layer under full‐inversion tillage (FIT). Our purpose was to review the literature in which SOC profiles have been measured under paired NT and FIT situations. Only replicated and randomized studies directly comparing NT and FIT for >5 yr were considered. Profiles of SOC had to be measured to at least 30 cm. As expected, in most studies SOC content was significantly greater (P < 0.05) under NT than FIT in the surface soil layers. At the 21‐ to 25‐cm soil depth, however, which corresponds to the mean plowing depth for the data set (23 cm), the average SOC content was significantly greater under FIT than NT. Moreover, under FIT, greater SOC content was observed just below the average depth of plowing (26–35 cm). On average, there was 4.9 Mg ha−1 more SOC under NT than FIT (P = 0.03). Overall, this difference in favor of NT increased significantly but weakly with the duration of the experiment (R2 = 0.15, P = 0.05). The relative accumulation of SOC at depth under FIT could not be related to soil or climatic variables. Furthermore, the organic matter accumulating at depth under FIT appeared to be present in relatively stable form, but this hypothesis and the mechanisms involved require further investigation.
Characteristics of Soil Carbon Buried for 3300 Years in a Bronze Age Burial Mound
Authors: Thomsen Ingrid K. , Kruse Tove , Bruun Sander , Kristiansen Søren M. , Knicker Heike , Petersen Søren O. , Jensen Lars S. , Holst Mads K. , Christensen Bent T.
Published: August 2008

To elucidate the mechanisms responsible for the long‐term retention of soil C, soil samples were retrieved from a paleosolic A h1orizon (Mbur) buried underneath a Bronze Age mound and from waterlogged anaerobic (Man) and aerobic zones (Mae) within the mound. For comparison with a modern soil, samples were taken from the surrounding arable field (Ar). The soils were characterized by cross‐polarization magic angle spinning13C nuclear magnetic resonance spectroscopy, by phospholipid fatty acid (PLFA) analysis, and by CO2production during incubation. At sampling, the Ar, Man, Mae, and Mbursoils contained 22.6, 17.9, 6.5, and 6.2 g C kg−1soil, respectively. Compared with the Ar and Mansoils, the Mburand Maesoils were depleted in alkyl C, N‐alkyl C, and O‐alkyl C and enriched in aromatic and carboxylic groups. The content of PLFA in the mound soils was much lower than normally found for arable soils and the ability of the deprived biomass to decompose glucose was retarded and included a 2‐ to 3‐wk lag phase. The lability of C left under aerobic conditions for more than three millennia did not differ significantly from that of C in the contemporary Ar soil. Although the chemical nature of the C in the Ar and Mansoils was similar, C that had resided under anaerobic conditions was less labile than C from the arable soil. We consider the persistence of C in the unwaterlogged parts of the burial mound to result from physical restrictions imposed on gas exchange and water availability, and thus restricted microbial activity, rather than from biochemical recalcitrance of the remaining C.
Comparison of Michigan and Dutch Podzolized Soils: Organic Matter Characterization by Micromorphology and Pyrolysis‐GC/MS
Authors: Buurman Peter , Jongmans Antoine G. , Nierop Klaas G. J.
Published: August 2008

Soil organic matter in a chronosequence of Michigan soils (Spodic Udipsamments and precursors) was studied in thin section and by pyrolysis‐gas chromatography/mass spectrometry (GC/MS). The Michigan soils were compared with a well‐drained Dutch Typic Haplorthod that was studied with the same methods. Both techniques indicate that most B‐horizon organic matter in the Michigan sequence is root‐ and char‐derived and not due to illuviation. Microbial matter contributes significantly to B‐horizon chemistry. Although charcoal is common in A horizons, it hardly contributes to soil organic matter (SOM) chemistry in this horizon, while it constitutes a significant part of B‐horizon C. This suggests that silt‐size particulate charcoal is transported downward. Nitrogen‐containing pyrolysis fragments are abundant, which, together with significant amounts of aromatic components, points to contribution of proteins. The Michigan soils are far less rich in alkyl C than the Dutch counterpart. This suggests a much lower residual accumulation of recalcitrant compounds in the former, probably due to a larger contribution of root litter and a more efficient decomposition. Faster decomposition (shorter mean residence time) in the Michigan soils is also suggested by the low accumulation of SOM in the B horizon. Thus we can conclude that in the Michigan soils, dissolved organic matter contributes significantly to transport of Al and Fe, but essentially without illuviation of organic matter in the B. In the Dutch Spodosol, on the other hand, both transport of dissolved organic C to the B horizon and accumulation of SOM through decomposition of roots play important roles. Pyrolysis‐GC/MS is a powerful tool in deciphering organic‐matter‐related aspects of soil genesis. The formation of many soils is organic matter driven, and this aspect is still poorly understood.
Nitrous Oxide Emissions Respond Differently to No‐Till in a Loam and a Heavy Clay Soil
Authors: Rochette Philippe , Angers Denis A. , Chantigny Martin H. , Bertrand Normand
Published: August 2008

The anticipated benefits of increased soil C stocks on net soil‐surface greenhouse gas (GHG) emissions after adoption of soil conservation practices can be offset by increases in soil N2O emissions. The objective of this study was to assess the short‐term impacts of no‐till (NT) on soil N2O emissions. The study was conducted in eastern Canada in the 3rd, 4th, and 5th yr after initiation of NT and fall moldboard plowing (MP) on heavy clay and gravelly loam soils. Annual emissions of N2O were exceptionally high in the heavy clay soil, varying from 12 to 45 kg N2O‐N ha−1 during the 3 yr of the study. Such high emissions were probably not associated with fertilizer N inputs but rather with denitrification sustained by the decomposition of large soil organic matter stocks (192 Mg C ha−1 in the top 0.5 m). On average, NT more than doubled N2O emissions compared with MP in the heavy clay soil. The influence of plowing on N2O flux in the heavy clay soil was probably the result of increased soil porosity that maintained soil aeration and water content at levels restricting denitrification and N2O production in the top 0.20 m. In the loam soil, average emissions during the 3 yr were similar in the NT and MP plots. The results of this study indicate that the potential of NT for decreasing net GHG emissions may be limited in fine‐textured soils rich in organic matter that are prone to high water content and reduced aeration.
Potassium Fertility and Terrain Attributes in a Fragiudalf Drainage Catena
Authors: Winzeler H. Edwin , Owens Phillip R. , Joern Brad C. , Camberato James J. , Lee Brad D. , Anderson David E. , Smith Doug R.
Published: August 2008

Site‐specific management of soil fertility has been based on soil sampling in grid patterns or within soil mapping units without taking full advantage of terrain–soil relationships. The goal of this study was to determine whether terrain attributes relate significantly to soil K availability. The topographic wetness index (TWI), a terrain attribute that comprises the upstream contributing area and the slope for a portion of land, relates to soil wetness. We evaluated Mehlich‐3 K (M3K), plant‐available nonexchangeable K (PANK) with a modified tetraphenylboron extraction, effective cation exchange capacity (ECEC), and other soil variables from soil samples taken at three depths, and terrain attributes in a 3.6‐ha farmed site in the Cincinnati catena, a major toposequence in the Muscatatuck Uplands region of Indiana. The PANK and M3K were significantly (P < 0.0001 and P < 0.05, respectively) related to TWI and relative elevation in models with anisotropic spatial autocorrelation variance estimates in three dimensions (latitude, longitude, and soil depth). The PANK and M3K increased with decreasing TWI in the following drainage class order: poorly < somewhat poorly < moderately well drained. The M3K decreased with soil depth, while PANK increased. The PANK/M3K ratio was significantly higher in the poorly drained soils than in the moderately well‐drained soils, implying greater mobility or weathering of K in wetter soils. The ECEC also related strongly to terrain attributes (P < 0.0001 for relative elevation, TWI, and interaction effects). Possible mechanisms include lateral downslope lessivage and K leaching. Terrain attributes can aid in soil K fertility evaluations on the Cincinnati catena because they relate well to soil K fertility measurements.
Organic Carbon Effects on Soil Physical and Hydraulic Properties in a Semiarid Climate
Authors: Benjamin Joseph G. , Mikha Maysoon M. , Vigil Merle F.
Published: August 2008

Increasing cropping intensity in the central Great Plains of the United States has the potential to increase organic carbon (OC) stored in the soil and lead to improved soil physical properties. A cropping systems study was started in 1990 at the Central Great Plains Research Station near Akron, CO. In 2005 soil samples were taken in six 95‐mm increments to a depth of 370 mm to measure OC, water stable macroaggregates (water stable aggregates > 250 μm), bulk density (ρb), total porosity (ϕtotal), water storage porosity (ϕws), and saturated hydraulic conductivity (ksat). Samples were collected from permanent grass plots {45% smooth brome [Bromus inermis (Leyss.)], 40% pubescent wheat grass [Agropyrons trichophorum (Link) Richt.], and 15% alfalfa [Medicago sativa (L.)]}, plots in a wheat {[Triticum aestivum (L.)]–corn [Zea mays (L.)]–millet [Panicum miliaceum (L.)]} rotation, and plots in a wheat–fallow rotation. Increased cropping intensity significantly increased OC, water stable macroaggregates, and ksat, but had no significant effect on ρb, ϕtotal, or ϕws Permanent grass increased OC compared with the annually cropped rotations, particularly deeper in the soil. Plots in permanent grass had greater ksat and this may indicate greater pore continuity and stability under saturated conditions. Organic carbon and water stable macroaggregates were poorly correlated. Water stable macroaggregates was negatively correlated with ρb and positively correlated with ksat Increasing soil OC may not immediately lead to changes in soil aggregation in a semiarid climate. Increased time and biological activity may be needed to convert the crop residues into organic compounds that stabilize aggregates and soil pore systems.
Modeling Copper(II) Complexation in a Peat Soil Based on Spectroscopic Structural Information
Authors: Karlsson Torbjörn , Elgh-Dalgren Kristin , Skyllberg Ulf
Published: August 2008

The speciation of Cu in soils and surface waters is largely influenced by complexation reactions with natural organic matter (NOM). In this study, ion selective electrode data for the binding of Cu2+ to a forest peat soil were collected as a function of equilibration time, pH (2.4–6.6), and total Cu(II) concentration (1–54g Cu kg−1 dry soil). As a first step, a one‐site Langmuir isotherm was successfully fitted to the Cu adsorption data for the complete concentration range at pH 4.6. In a second step, structural information extracted from extended x‐ray absorption fine structure (EXAFS) spectroscopy, showing that Cu(II) forms five‐membered rings with possible combinations of amine, carboxyl, and carbonyl functional groups in NOM, were used as input for chemical speciation calculations (using the chemical equilibrium model MINTEQA2). In agreement with the EXAFS results, a model consisting of one RNH2, forming monodentate complexes (Cu2+ + RNH2 ↔ RH2NCu2+; log stability constant KRH2NCu2+ = 9.2; −log acid dissociation constant [pKa] = 9.0 for RNH3+), and two adjacent RCOO− groups, forming bidentate complexes (Cu2+ + 2RCOO− ↔ Cu(OOCR)2; log stability constant β(RCOO)2Cu = 4.7; pKa = 4.5 for RCOOH), gave the best fit to the experimental data. Determined stability constants for Cu(II)–amine and Cu(II)–carboxyl complexes were in good agreement with well‐defined Cu complexes with amino acids and carboxyls, respectively.
Isotopic Exchangeability, Hydrolysis and Mobilization Reactions of Pyrophosphate in Soil
Authors: McBeath T. M. , Lombi E. , McLaughlin M. J. , Bünemann E. K.
Published: August 2008

Liquid polyphosphate fertilizers have shown significant yield increases compared with granular orthophosphate fertilizer on highly P‐fixing soils in Australian cropping trials. Polyphosphate fertilizers contain mixed P species (predominantly pyrophosphate and orthophosphate) and are therefore chemically different from most other inorganic P fertilizers, which contain only orthophosphate. To determine the mechanisms causing the yield responses to polyphosphate fertilizer, a method for investigating the isotopic exchangeability (lability) of P added as pyrophosphate was developed and tested. This method enabled the quantification of the hydrolysis reaction of pyrophosphate to orthophosphate in soil solution. As the rate of pyrophosphate applied increased, the proportion of pyrophosphate added that was isotopically exchangeable increased, and the percentage of pyrophosphate added that hydrolyzed to orthophosphate decreased. The method was further developed to test the hypothesis that pyrophosphate addition to soil may cause the mobilization of native orthophosphate reserves. The results suggested that there was no mobilization of native P after 7 d of incubation in two calcareous soils.
Surface Albedo and Soil Heat Flux Changes Following Drilling Mud Application to a Semiarid, Mixed‐Grass Prairie
Authors: Zvomuya Francis , Larney Francis J. , McGinn Sean M. , Olson Andrew F. , Willms Walter D.
Published: August 2008

Drilling mud systems are used by the petroleum industry to facilitate and expedite the drilling of oil and natural gas wells. In western Canada, spent water‐based muds (WBM) are often applied to cropland and native prairie at low application rates as a disposal option. We speculate that application of drilling waste on native prairie in semiarid climates will alter the soil surface energy balance and adversely affect soil biophysical processes and subsequently ecosystem productivity. This study was initiated to examine the effect of application rate (0, 40, and 80 m3 ha−1) of summer‐applied WBM on surface albedo (α), soil temperature, and soil heat flux at the 0.05‐m depth (G0.05) and at the surface (G) over 42 d following application. Our results provide evidence of a significant alteration of these micrometeorological parameters with WBM application. Surface albedo decreased by 15% (relative to the control) with the application of 40 m3 ha−1 mud and by an additional 3% when this mud rate was doubled. The lower α meant that a greater proportion of incoming shortwave solar radiation (Rsi) was available for partitioning into components of the surface energy balance, including G This coincides with observed increases in G0.05, G, and soil temperature at the 0.025‐m depth, with higher WBM. By modifying heat flow and temperature in the root zone, WBM application may alter critical ecosystem biophysical and physiological processes, with important implications for overall biological productivity. The direction and magnitude of such changes, in conjunction with all the other ecological effects of WBM, will ultimately define the sustainability of the practice in this fragile ecosystem.
Pathogen and Indicator Organism Reduction Through Secondary Effluent Filtration: Implications for Reclaimed Water Production
Authors: Levine Audrey D. , Harwood Valerie J. , Farrah Samuel R. , Scott Troy M. , Rose Joan B.
Published: August 2008

The reduction of pathogens and indicator organisms through secondary effluent filtration was investigated at six full‐scale treatment facilities, ranging in capacity from 0.04 to 1 m 3/s (1 to 25 mgd). Grab samples were assayed for pathogens (cultivable enteric viruses, Giardia, and Cryptosporidium) and indicator organisms (coliforms, enterococci, Clostridium perfringens, and coliphages) quarterly under peak flow conditions from each facility over the course of 1 calendar year. Log 10 removals resulting from filtration averaged 0.3 to 0.8 log 10 for cultivable enteric viruses, 0.4 to 1.5 log 10 for protozoan parasites, 0.01 to 3.7 log 10 for indicator bacteria, and 0.3 to 1.1 log 10 for coliphages. In addition to filter design (cloth, monomedium shallow‐ or deep‐bed, or dual‐media filters), differences in reduction of pathogens and indicators could be attributed to the combined effects of hydraulic loading rates, chemical addition practices, backwashing and postbackwashing operating strategies, and the effectiveness of upstream biological treatment and sedimentation.
Improved Computational Model (AQUIFAS) for Activated Sludge, Integrated Fixed‐Film Activated Sludge, and Moving‐Bed Biofilm Reactor Systems, Part II: Multilayer Biofilm Diffusional Model
Authors: Sen Dipankar , Randall Clifford W.
Published: August 2008

Research was undertaken to develop a diffusional model of the biofilm that can be applied in lieu of a semi‐empirical model to upgrade an activated sludge system to an integrated fixed‐film activated sludge (IFAS) or moving‐bed biofilm reactor (MBBR) system. The model has been developed to operate with up to 12 cells (reactors) in series, with biofilm media incorporated to one or more of the zone cells, except the anaerobic zone cells.    The values of the kinetic parameters for the model were measured using pilot‐scale activated sludge, IFAS, and MBBR systems. The biofilm is divided into 12 layers and has a stagnant liquid layer. Diffusion and substrate utilization are calculated for each layer. The equations are solved simultaneously using a finite difference technique. The biofilm flux model is then linked to the activated sludge model. Advanced features include the ability to compute the biofilm thickness and the effect of biofilm thickness on performance. The biofilm diffusional model is also used to provide information and create a table of biofilm yields at different substrate concentrations that can be used in the semi‐empirical model.