bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphorus Desorption Quantity‐Intensity Relationships in Soils
Authors: Raven K. P. , Hossner L. R. 
Published: July 2010

AbstractPhosphorus desorption quantity‐intensity (Q/I) relationships reveal information about the P release properties of a soil. This research was carried out to evaluate the P desorption characteristics of a group of soils of diverse properties and to compare several empirical models to describe P desorption Q/I curves. Samples of five soils (Typic Calciustoll, Udic Pellustert, Vertic Albaqualf, and Aridic Calciustoll surface soils, and Psammentic Paleudult subsoil) were enriched with five P concentrations (0, 25, 50, 75, and 100 mg P kg−1) and incubated for 31 d. Subsamples of each treated soil sample were equilibrated with different amounts of HCO−3‐saturated anion‐exchange resin. After 72 h the amount of P sorbed on the resin (Q) as well as the solution P concentration (I) were determined. Results from each subsample gave a point on the Q/I curve. The P release capacity of the soils used in this study was relatively low. In untreated samples, the solution P concentration when no P was desorbed (Io), an intensity parameter, ranged between <0.01 and 0.19 mg P L−1, while the maximum desorbed soil P (Qmax), a quantity parameter, was in the range 4.7 to 21.1 mg P kg−1. The corresponding P buffering power index, the slope of the Q/I curve at Io, ranged between 56 and 1703 L kg−1. These Q/I parameters were not closely related to any evaluated soil property, with the possible exceptions of CaCO3 content in calcareous soils and clay content. The P buffering power of a soil apparently depended on the availability of P sorption sites and their degree of depletion, and was not always directly related to the ability of a soil to release P. The P release activity of a P‐enriched soil depended on the desorbability of the applied P as well as the native labile soil P. Plots of P buffering power against intensity for a given soil were not affected by P enrichment. The Q/I curves could be best described by a proposed desorption Q/I equation (Q = a I−0.1 + b ln(I + 1) + c) and the Barrow power function, but the proposed equation followed the theoretical expected trend. The proposed equation is therefore recommended to describe P desorption Q/I curves.
Sericites in Feldspars as Source of 2:1 Phyllosilicates in Selected Sandy Soils
Authors: Arocena J. M. , Pawluk S. , Dudas J. M. 
Published: July 2010

AbstractThe high content of 2:1 phyllosilicates in the eluvial horizon of many sandy forested soils in North America is attributed to extraneous deposition. In this study, we evaluated the hypothesis that sericite in feldspars is a local source of 2:1 phyllosilicate by investigation of thin sections and coarse sand fractions from three pedons in an Alfisol‐Spodosol association developed on Quaternary sandy deposits in Alberta. In situ investigation of the alteration products of feldspar weathering was conducted by using x‐ray microdiffraction techniques, light and electron microscopy, and layer charge density by alkyl ammonium saturation technique. The nature of the minerals in the bulk samples and total elemental composition of the sand fractions were also investigated. Results showed that feldspars occur as orthoclase, microcline, and albite. Some of the feldspar grains were perthitic in nature. The weathering of feldspars is characterized by linear striations (parallel and cross linear) and starts mainly from grain fractures and twin planes. Several types of 2:1 phyllosilicates were identified in the alteration products: (i) a component with a fixed basal spacing around 1.0 nm, (ii) a high‐charge component with a charge density of about 0.6 molc [(Si, Al)4O10]−1, (iii) a low‐charge component with charge density of about 0.34 molc [(Si, Al)4O10]−1, and (iv) an interstratified component comprising of both the low‐ and high‐charge components.
Electrophoretic Mobility and Particle Size of Clays Using Laser Doppler Velocimetry‐Photon Correlation Spectroscopy
Authors: Anderson M. A. , Bertsch P. M. 
Published: July 2010

AbstractLaser Doppler velocimetry‐photon correlation spectroscopy (LDV‐PCS) was evaluated for the characterization of clay minerals. Electrophoretic mobility and particle size of pure and mixed suspensions of KGa‐2 kaolinite and SWy‐1 bentonite were determined as a function of pH, ionic strength, and suspension concentration ratios. Kaolinite mobility changed from significant positive values at low pH to negative values at high pH, consistent with the variable‐charge nature of kaolinite. Evidence for a contribution of positive charge originating at bentonite edges at low pH (<4) was also found. Ionic strength also affected mobility of kaolinite and, at low pH, bentonite. Mixtures of kaolinite and bentonite at low pH yielded mobility distribution spectra intermediate to those of the component clays. The two populations were not resolved, which suggests that the kaolinite and bentonite formed mixed particle associations. Particle‐size analyses supported inferences from mobility data that significant particle‐particle association occurred under neutral to low pH and moderate ionic strength conditions.
Measuring In Situ Changes in Labile Soil Phosphorus with Anion‐Exchange Membranes
Authors: Cooperband L. R. , Logan T. J. 
Published: July 2010

AbstractConventional chemical extraction methods to measure labile soil P are often inadequate for detecting fine temporal‐ and spatial‐scale soil P dynamics in situ. We refined and calibrated methodology for anion‐exchange resin‐impregnated membranes (AEM), related AEM‐P to soil solution P for a high‐P‐retaining soil, and evaluated the method's viability under humid tropical field conditions. We determined: (i) AEM recyclability, (ii) AEM P sorption kinetics, (iii) the correlation between soil solution P and AEM‐P for an Andic Humitropept, and (iv) potential interference from other anions (NO−3 and SO2−4) on AEM P extraction. We used AEMs in a field decomposition study to evaluate plant residue and manure P release characteristics and concurrent fluxes in labile soil P. The AEM P sorption capacity was not altered significantly by repeated use. Nitrate solution concentrations in an aqueous medium of 50 and 100 mg NO3‐N/L reduced AEM P sorption by 50 and 75%, respectively, regardless of P solution concentration; SO4‐S at 500 and 1000 mg/L reduced AEM P sorption by ≈98%. The relationship between AEM‐P and soil solution P was curvilinear at both nonequilibrium and equilibrium soil solution P concentrations; it was essentially linear at soil solution concentrations ranging from 0 to 2 mg P/L. The AEM behaved as a dynamic exchanger rather than an infinite sink for P, particularly in the context of a low‐pH, high‐P‐retaining soil. The AEMs detected biologically relevant soil P pulses in the field decomposition study. The technique holds promise as an easy method for measuring soil P fluxes with minimal soil disturbance.
Conveyor‐Belt Apparatus for Fine Grinding of Soil and Plant Materials
Authors: Kelley K. R. 
Published: July 2010

AbstractRecent advances in instrumentation have provided the capability to determine total N and 15N concentrations in milligram quantities of soil or plant material. Analytical precision with small samples is adversely affected by sample heterogeneity, however, and fine sample grinding is necessary. A grinding apparatus using a conveyor‐belt assembly and operating as a roller mill was developed. The samples are ground and stored in the same bottle, reducing the risk of cross contamination, and up to 55 samples can be processed simultaneously. Corn (Zea mays L.) leaf, bermudagrass [Cynodon dactylon (L.) Pers. var. dactylon], and soil were finely ground in 12 h or less, but longer grinding periods are recommended for hard‐to‐grind materials such as corn grain and corn cobs. Analytical precision for measurement of total N and 15N concentrations by direct‐combustion, continuous‐flow mass spectrometry tended to increase with decreasing particle size.
Sodic Soil Toposequence Related to Focused Water Flow
Authors: Seelig B. D. , Richardson J. L. 
Published: July 2010

AbstractPresent concepts of sodic soil formation do not adequately account for observed variability of sodic soil properties on many landscapes in North Dakota. A conceptual model was developed to explain sodic soil genesis related to water and salt movement on a coarse‐loamy till landscape in central North Dakota. The relationship between subsurface water flow and sodic soils was determined by monitoring soil water using neutron attenuation and water wells at three contiguous landform positions. Electrical conductivity, major ions, and water‐dispersible clay were determined on extracts from selected soil samples from each landform position. Typic Argiaquolls, characterized by low salinity (electrical conductivity [EC] < 2.0 dS/m), occurred at the wetland position and were areas of recharge to groundwater. Typic Natraquolls also occurred at the wetland position but were characterized by high salinity (EC > 5.0 dS/m) and were areas of groundwater discharge. Udic and Leptic Natriborolls were areas of groundwater discharge at the intermediate and upland positions. Udic Haploborolls were hydrologically inactive areas at the upland position. Variations in sodic soil development were attributed to the concentration of water flow (focused flow) into specific areas of groundwater discharge or recharge. The most important factors that affected the direction and intensity of focused flow were stratigraphy and landform position.
Long‐Term Effects of Forest Fertilization on Site Organic Matter and Nutrients
Authors: Harding R. B. , Jokela E. J. 
Published: July 2010

AbstractThe long‐term effects of time‐of‐planting fertilization on the accumulation and distribution of above‐ and belowground organic matter and nutrients are largely unknown for intensively managed southern pine (Pinus spp.) stands in the U.S. lower Coastal Plain. These effects were investigated using a 25‐yr‐old slash pine (P. elliottii Engelm. var. elliottii) plantation in north Florida. The experiment was conducted on a poorly drained, P‐deficient Rutlege soil (sandy, siliceous, thermic Typic Humaquept) using a randomized complete block design. The experimental treatments included: (i) control, (ii) NPK (112, 39, and 45 kg ha−1 using ordinary superphosphate [OSP] + N and K) and (iii) P (314 kg P ha−1 using ground rock phosphate [GRP]). Fertilization significantly increased total aboveground organic matter accumulation, with levels for the OSP + NK and GRP treatments being 2.5 and 1.8 times greater than the control, respectively. Levels of soil organic matter measured to a depth of 91 cm did not vary, however. Treatment effects were found for P, K, and Ca levels in the fertilized slash pine biomass components and surface soil. Long‐term differences in extractable soil P were most pronounced for the GRP treatment, with concentrations in the surface 15 cm being 2.6 times greater than the control; only the high P treatment sustained foliar P levels within the published critical range for slash pine. While field trials are required to confirm actual fertilizer carryover effects, results from this experiment suggest that sites previously fertilized with operational P rates (40–80 kg ha−1) will again require treatment when establishing the next pine rotation.
Nitrogen and Phosphorus Interactions in an Intensively Managed Nursery Soil‐Plant System
Authors: Teng Y. , Timmer V. R. 
Published: July 2010

AbstractNitrogen in forest tree nurseries is usually applied as topdressing during the growing season, while P is incorporated in the soil before seeding. Combined N and P topdressing as monoammonium phosphate (MAP) may improve nursery stock production. To test this practice, white spruce [Picea glauca (Moench) Voss] seedlings top‐dressed with MAP, or factorial combinations of ammonium nitrate (AN) and phosphoric acid (PA) were grown for two seasons in a loamy sand nursery soil. Seedlings receiving AN alone increased in biomass (34%) but took up less P despite relatively high available P (310 mg kg−1) in the bulk soil. Phosphorus additions stimulated growth (107%) and also N and P uptake. Equivalent N dosages, as MAP or AN + PA, increased dry matter production by 362%, demonstrating a significant positive N × P interaction. Two nutritional responses seem to be involved in this interaction: (i) a countering of N antagonism on P uptake when N only was applied, and (ii) a synergistic effect of N and P uptake when these nutrients were applied together. Lower specific absorption rates of roots and suspected depletion of rhizospheric P probably accounted for the antagonistic effect in N‐only treatments, while increased root absorption efficiency and higher P availability in addition to the N supplied in N + P treatments contributed to the synergistic interaction. The N + P treatments resulted in lower seasonal NH4‐N and NO3‐N levels in subsoil than those from N‐only treatments, suggesting less leaching of N from combined N and P topdressings.
Measurement of Solute Transport during Constant Infiltration from a Point Source
Authors: Kachanoski R. G. , Thony J. L. , Vauclin M. , Vachaud G. , Laty R. 
Published: July 2010

AbstractTheory describing transport from a point source is well developed, but not tested because of the lack of experimental data. There are few field studies because sampling requires either destructive soil coring or vacuum solution samplers. The objective of this study was to develop a method of measuring quickly and nondestructively the vertical flux of solute below a drip (point) source of water. The method uses vertically installed time domain reflectometry (TDR) probes making it appropriate for field studies. Water is dripped between the vertical probes at a constant rate until the wetting front has passed the ends of the probes and the measured soil water content is not changing. At this time, the water source is switched to one with a constant concentration of electrolyte tracer, dripping at the same rate. The relative change in TDR impedance is related to the advance of the solute front. Thus, measurements of average solute velocity and cumulative travel time as a function of depth are obtained. At a low drip rate into a sandy soil, the measured advance of the solute front vs. the cubed root of time was similar to that predicted from the theory of gravity‐free infiltration. Identical measurements were obtained for the advance of solute‐free water into a soil with a high background concentration of solute. Methods of estimating solute dispersivity and the relative influence of gravity vs. capillarity from the measurements were suggested but not tested. In particular a method of estimating α, the ratio of hydraulic conductivity and matric flux potential, is suggested using existing solutions of the linearized equation for flux from a point source.
Glucose‐1‐phosphate and Myo‐inositol Hexaphosphate Adsorption Mechanisms on Goethite
Authors: Ognalaga M. , Frossard E. , Thomas F. 
Published: July 2010

AbstractThis research was performed to elucidate the adsorption mechanisms of two monoester phosphates, glucose‐1‐phosphate (G1P) and myo‐inositol hexaphosphate (I6P), on a synthetic goethite with reference to orthophosphate (Pi). Adsorption isotherms were built and electrophoretic and pH measurements were carried out in order to determine the nature of the adsorbent‐adsorbate bonds. The quantity of adsorbed compound reached 5.41 µmol Pi m−2, 5.06 µmol G1P m−2, and 1.37 µmol I6P m−2. The G1P and I6P were adsorbed on the surface hydroxyls of goethite through their phosphate groups. The proposed adsorption mechanism, notwithstanding the nature of the organic moiety, is a specific adsorption by a ligand exchange between the phosphate groups and the surface reactive hydroxyls. Inner‐sphere surface complexes are formed between phosphate groups and Fe. Very little dissolution of the goethite occurred during the adsorption of either of the two ligands (G1P and I6P). Tentative configurations of the formed organophosphate‐goethite complexes are proposed.
Calibration of Glass Microelectrodes for in Situ pH Measurements
Authors: Yang J. , Blanchar R. W. , Hammer R. D. 
Published: July 2010

AbstractGlass pH‐sensitive microelectrode fabrication, calibration, and measurement techniques have been altered to improve the applicability of the method. Insulating pipettes with inner filaments were drawn to 20‐µm tips and welded to the pH‐sensitive glass so the inner filament was not sealed. The filament allowed air to be displaced as the filling solution flowed to the pH‐sensitive tip, eliminating the need for a vacuum filling procedure. In situ calibration allowed soil pH to be measured without moving the reference electrode and altering the junction potential. Calibration is done in the same soil sample with the electrodes placed at a distance >5 cm from the site of pH measurement. The pH‐sensitive microelectrode is positioned above the soil close enough to make electrical contact. Two 0.05‐mL drops of pH buffer are added so that the drops flow down the electrode shaft to the soil as the electrode potential is measured. Soil pH values obtained by calibrating the electrodes in pH buffer solutions were 0.2 pH unit lower than those obtained by in situ calibration.The reference electrode contacted the soil through a saturated KCl salt bridge placed in the moist soil. At soil water potentials below saturation, better electrical contact is made when the soil‐salt bridge contact point is wetted with water, 1 mol L−1 KCl, or 0.01 mol L−1 CaCl2.
An Automated Microcosm System for Studying Soil Ecological Processes
Authors: Hantschel Ralph E. , Flessa Heiner , Beese Friedrich 
Published: July 2010

AbstractSoil ecological processes are characterized by high temporal and spatial variability. To evaluate effects of soil management and environmental parameters on single processes, it is necessary to investigate several replicates of each soil type under controlled laboratory conditions. We developed a microcosm system in which 64 disturbed or undisturbed soil columns, each controlled individually, may be evaluated. The technical design of the automated microcosm system demonstrates the broad applicability of the system. For demonstration the effects of the herbicide terbuthylazin (TA) on microbial respiration in microcosms treated with and without barley (Hordeum vulgare L.) straw are shown. Even high amounts of the herbicide applied did not reduce the CO2 release by the soil organisms. The C source added with the barley residues did not change this result significantly.
Accumulation of Fertilizer Nitrogen‐15 by Rice at Different Stages of Development
Authors: Guindo D. , Wells B. R. , Norman R. J. 
Published: July 2010

AbstractResults from fertilizer N recovery experiments with 15N have indicated high values of fertilizer 15N lost by rice (Oryza sativa L.). Field experiments were conducted to evaluate uptake of fertilizer 15N applied at preflood and at midseason and to determine the growth stage for maximum recovery of fertilizer 15N by rice under a dry‐seeded culture system. Aboveground plant portions were sampled throughout the season for total dry matter, total N, and fertilizer 15N. Total N accumulation when N was applied in a single preflood application was maximum at heading + 21 d and then declined at maturity. When N was applied at preflood and midseason, total N accumulation continued until maturity. Fertilizer 15N recovered in the rice plant from the preflood N application was maximum (62%) at 21 d after application, and declined 10% by maturity. Fertilizer 15N from the midseason N application had maximum recovery (75%) in the rice plant at 7 d after application, and declined by 18% by maturity. Accumulation of total N in the panicle between heading + 21 d and maturity for the midseason N application was significant; however, it was nonsignificant for the preflood N application. Recovery of fertilizer 15N in the panicle did not differ between heading + 21 d and maturity for either the preflood or midseason N application. These results confirm earlier findings that sampling plants only at maturity will underestimate maximum fertilizer 15N uptake by rice.
Edge Complexation Reactions of Cadmium on Specimen and Soil‐Derived Smectite
Authors: Zachara J. M. , Smith S. C. 
Published: July 2010

AbstractThe contribution of edge‐complexation reactions to metal ion sorption by smectites has not been well documented through experimentation or modeling. A model containing fixed‐charge (X−) and hydroxylated edge sites (AlOH and SiOH) was applied to sorption data for Cd on SWy‐1 smectite and a smectitic soil isolate in Na+, Ca2+, and mixed electrolytes to evaluate the potential contributions of ion exchange and surface coordination to metal cation binding. Sorption modeling was performed with FITEQL. Edge reactions were described using the triple‐layer model (TLM) and an inner sphere Cd complex on AlOH sites and outer sphere complexes on SiOH sites. The complexation reactions were parameterized using (i) Cd sorption data from silica and alumina and (ii) site concentration estimates based on cation‐exchange capacity (X−) and particle size measurements (AlOH and SiOH). Ion‐exchange reactions were described in half‐reaction format; exchange constants were fit using Cd sorption data in either Na+ or Ca2+ electrolyte. The sorption data was qualitatively described across ranges in pH and electrolyte concentration using a combination of ion exchange (CdX2) and edge (AlOCd+) complexes. Complexation of Cd to edge SiOH was calculated to be unimportant. The calculated contribution of AlOCd+ complexes increased with increases in pH and ionic strength. Good predictions of Cd sorption in mixed electrolytes were obtained using constants derived from single‐electrolyte systems. Edge sorption reactions were computed to be more important for the soil smectite than for SWy‐1 because of its smaller particle size. However, the slope and magnitude of sorption on the soil isolate was inadequately described by the model. Competitive sorption reactions on the edge sites and binding to organic material are additional factors that must be considered to adequately describe Cd sorption to smectitic soil clays.
Water‐Stable Aggregates and Organic Matter Fractions in Conventional‐ and No‐Tillage Soils
Authors: Beare M. H. , Hendrix P. F. , Coleman D. C. 
Published: July 2010

AbstractNo‐tillage (NT) practices can improve soil aggregation and change the distribution and retention of soil organic matter (SOM) compared with conventional tillage (CT), but the relationships between aggregates and SOM fractions are poorly known. The effects of long‐term (13‐yr) CT and NT management on water‐stable aggregates (WSA) and aggregate‐associated SOM were investigated on a Hiwassee sandy clay loam (clayey, kaolinitic, thermic Rhodic Kanhapludult). Samples were collected at two depths in replicated CT and NT plots and separated into five aggregate size classes by wet sieving. The stability of intact WSA was measured turbidimetrically. The C and N content of total, particulate (POM), and mineral‐associated organic matter was determined for each size class. Whole‐soil organic C was 18% higher in NT (30.7 Mg C ha−1) than in CT (26.1 Mg C ha−1). In CT, macroaggregates (>250 µm) were fewer and less stable than those of NT. The POM C made up ≈36% of whole soil C regardless of tillage, but the quantity of POM was nearly 20% higher in NT than in CT. The POM comprised a higher percentage of total aggregate N in surface soils of NT than in CT and values increased with increases in aggregate size. In NT, concentrations of total and mineral‐associated C and N were higher in the 106‐ to 250‐µm WSA than in the other size classes but, in CT, the concentrations were similar among size classes. An alternative view of aggregate organization is discussed in which microaggregates are formed in association with POM at the center of macroaggregates, helping to explain relationships between SOM storage and aggregate size distributions under different management practices.