bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Autocorrelation and Measurement Errors on Interpretation of Solubility Diagrams
Authors: Xu Shihe , Harsh James B. 
Published: July 2010

AbstractThe solubility method for determining solid‐phase controls on solute activities in aqueous systems is subject to potential sources of misinterpretation. Measurement errors cause deviation of solid‐phase solubilities from theoretical values, whereas autocorrelation between dependent and independent variables of a solubility diagram may lead to false interpretation of data points falling on a given solubility line. In this study, a Monte Carlo simulation was performed to determine the influence of measurement errors and autocorrelation on the interpretation of solubility data. For solid‐phase control of Al activity at pH <6 for natural gibbsite, basaluminite, and jurbanite, deviation of apparent solubility from theoretical solubility lines of the solids due to measurement errors in pH, total inorganic monomeric Al, ionic strength, and SO4 activity are usually small compared with the deviation expected when random numbers are used to generate a data set. As a result, solid‐phase control was distinguishable from autocorrelation of random data except at pH 6 to 7. For a given metal oxide, autocorrelation interference is significant in a solubility study only when the OH/metal ratio of the predominant dissolved metal species is close to the OH/metal or O/Metal ratio of the solid phase. We concluded that the solubility method is a reliable and useful tool to study Al chemistry in acid soils if used with caution.
Micromorphology of Pedogenically Derived Fracture Fills in Bandelier Tuff, New Mexico
Authors: Davenport David W. , Wilcox Bradford P. , Allen B. L. 
Published: July 2010

AbstractFractures in the Bandelier Tuff are potential paths for water movement and transport of contaminants from waste disposal sites and other contaminated areas at Los Alamos National Laboratory, Los Alamos, NM. Contaminants transported in this way could ultimately be found in Los Alamos drinking water or in the Rio Grande, which flows through heavily populated areas in both the USA and Mexico. We conducted this study to determine (i) the morphology and origin of soil‐like material in the fractures, and (ii) the likelihood of significant water movement through the fractures. We examined thin sections of fracture fills, soils, and tuffs to obtain fabric and mineralogical data, and collected field data on soil horizons, color, texture, structure, clay films, and root abundance. Fracture fills consist of clay, CaCO3, or combinations of the two with minor inclusions of tuff and sand grains. Clay consists of thick, highly oriented argillans aligned parallel to fracture walls, and of discrete books in fracture interiors. Carbonate consists of massive microcrystalline calcite, which completely fills some fractures, and laminae or infillings between clay laminae or books in clay‐dominated fractures. The carbonate was precipitated after clay deposition, suggesting a change to a more arid climate. Weaker development of argillans and carbonate features in the soils suggests that the fractures may be derived from older soils that have been stripped by erosion. The presence of live roots throughout the fracture fills indicates the presence of water, but the smectitic clay and massive carbonate make it unlikely that significant water movement is now taking place through the fractures. The potential creation of new macropores by a variety of processes, however, including seismic activity and biologic disturbance, could allow rapid water movement and contaminant transport.
Organic Anions' Effect on Phosphorus Release from Spodic Horizons
Authors: Lan Mu , Comerford N. B. , Fox T. R. 
Published: July 2010

AbstractThe purpose of this research was to investigate the release of P from the spodic horizons of common forested soils in the Lower Coastal Plain of Florida and Georgia. This was considered important because (i) these soils have a history of variable responses to P fertilization, (ii) roots are known to grow in this material, and (iii) previous research has suggested that the P in this material might be available to plants. Desorption experiments using 0.001 M concentrations of a variety of organic ligands (pH 4.3 for initial solutions) with a range of Al complexation constants were conducted by reacting the ligand solutions with spodic horizon soil. Inorganic P, organic P, and Al were measured in the resulting extracts. Results showed that the amount of extractable inorganic P in these soils was variable. Some soils had detectable levels of extractable inorganic P, while others are essentially devoid of it. In those soils that had extractable P, the inorganic P release was correlated to the release of Al as the release of both moieties was initiated by organic anions with logKAl values, the Al stability constant with that anion, of about 3.2 to 4.2 or greater. This suggests that root exudates with logKAlS less than these values would not be effective in making inorganic P in spodic horizons more available to plants. Organic P is a major component of the soil solution and is released by a mechanism unrelated to the logKAl of the organic ligand.
Improved Method for Measuring Water Imbibition Rates on Low‐Permeability Porous Media
Authors: Humphrey M. D. , Istok J. D. , Flint L. E. , Flint A. L. 
Published: July 2010

AbstractExisting methods for measuring water imbibition rates are inadequate when imbibition rates are small (e.g., clay soils and many igneous rocks). We developed an improved laboratory method for performing imbibition measurements on soil or rock cores with a wide range of hydraulic properties. Core specimens are suspended from an electronic strain gauge (load cell) in a closed chamber while maintaining the lower end of the core in contact with a free water surface in a constant water level reservoir. The upper end of the core is open to the atmosphere. During imbibition, mass increase of the core is recorded continuously by a datalogger that converts the load cell voltage signal into mass units using a calibration curve. Computer automation allows imbibition rate measurement on as many as eight cores simultaneously and independently. Performance of each component of the imbibition apparatus was evaluated using a set of rock cores (2.5 cm in diameter and 2–5 cm in length) from a signle lithostratigraphic unit composed of non‐to‐moderately welded ash‐flow tuff (a glass‐rich pyroclastic rock partially fused by heat and pressure) with porosities ranging from 0.094 to 0.533 m3 m‐3. Reproducibility of sample handling and testing procedures was demonstrated using replicate measurements. Precision and accuracy of load cell measurements were assessed using mass balance calculations and indicated agreement within a few tenths of a percent of total mass. Computed values of sorptivity, S, ranged from 8.83 × 10‐6 to 4.55 × 10‐4 m s‐0.5. The developed method should prove useful for measuring imbibition rates on a wide range of porous materials.
Nonexchangeable Ammonium and Potassium Determination in Soils with a Modified Sodium Tetraphenylboron Method
Authors: Cox A. E. , Joern B. C. , Roth C. B. 
Published: July 2010

AbstractThe mechanism of NH+4 and K+ fixation by clay minerals is similar, yet different analytical methods are used to estimate nonexchangeable (fixed) amounts of these nutrients in soils. Sodium tetraphenylboron (NaBPh4) facilitates the release of nonexchangeable NH+4 and K+ by precipitation of these ions as NH4BPh4 and KBPh4. A NaBPh4 method was modified and evaluated as a common procedure for determination of nonexchangeable NH+4 and K+ in 10 midwestern soils that were either untreated or NH+4 − or K+‐saturated (treated with 2 M solutions of NH4Cl or KCl to saturate fixation sites with NH+4 or K+). Experiments were conducted to evaluate Cu2+ (CuCl2) as a substitute for Hg2+ (HgCl2) in the recovery of NH+4 and K+ released by NaBPh4 in soils. A 7‐d incubation with the modified NaBPh4 method (CuCl2 instead of HgCl2) released most of the NaBPh4‐ extractable NH+4 and K+. In untreated soils, the NaBPh4 method extracted 71% of NH+4 released by the conventional HF/HCl method. Nonexchangeable NH+4 release by both methods was related in untreated (r2 = 0.98) and NH+4‐saturated (r2 = 0.95) soils. Recently fixed NH+4 in the NH+4‐saturated soil was equally accessible to both methods. The NaBPh4 method extracted up to 10 times more nonexchangeable K+ than the conventional 1 M HNO3 method in both the untreated and K+‐saturated soils. Recently fixed K+ in the K+‐saturated soil was equally accessible to both methods, except in high‐fixing soils where K+ was held too strongly to be released by HNO3. The results show that the modified NaBPh4 method can be used as a common procedure to estimate nonexchangeable forms of both NH+4 and K+.
Incorporating Nonextractable Atrazine Residues into Soil Size Fractions as a Function of Time
Authors: Barriuso E. , Koskinen W. C. 
Published: July 2010

AbstractSoil organic matter is directly implicated in pesticide nonextractable (bound) residues formation, but the role of different soil organic constituents is unknown. Physical soil fractionation allows separation, with minimal chemical modification, of organic constituents whose nature and properties are dependent on particle size. Physical fractionation was used to determine the role of soil organic constituents in atrazine (6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine) bound residues formation. 14C‐ring‐labeled atrazine was applied to the top of soil lysimeters (0.3 by 1.2 m) in the field. The lysimeters were periodically removed during 16 mo, and the soil was physically fractionated into seven size fractions by sieving, sedimentation, and centrifugation: >200, 50 to 200, 20 to 50, 5 to 20, 2 to 5, 0.2 to 2, and <0.2 µm. The largest proportion of total bound residues in the whole soil was in the clay size (0.2–2 µm) fraction, which also contained 50% of the total soil organic C (OC). The ratio of bound residues to OC content decreased with the particle size, and it was highest in fractions >50 µm, those rich in nonhumified organic matter. The low capacity of humified organic matter in the finest size fractions to form bound residues is presumably due to the chemical nature of the humified organic matter; however, accessibility of organic compounds stabilized on the fine mineral surfaces or included in aggregates structures is also a possibility. The most stable bound residues are associated with humified organic matter, especially in clay size fraction (0.2–2 µm). Physical soil fractionation as a function of incubation time allows definition of the different capacity of soil organic constituents to form bound residues in relation to their localization in the size fractions.
Porosity Factors that Control the Hydraulic Conductivity of Soil‐Saprolite Transitional Zones
Authors: Vepraskas M. J. , Kleiss H. J. , Amoozegar A. , Guertal W. R. 
Published: July 2010

AbstractSlowly permeable transitional horizons separate soil and saprolite, but these horizons cannot be identified easily in the field. The objectives of this study were to determine why the soil‐saprolite transitional zone (BC and CB horizons) is slowly permeable, and to evaluate ways for identifying it in the field. Two saprolite deposits were studied in the North Carolina Piedmont. At each site, saturated and unsaturated hydraulic conductivities (Ksat and Kunsat) were measured for major horizons. Volume fractions of water‐conducting pores were also compared with the changes in hydraulic conductivity with depth. Horizon mean Ksat values at both sites ranged from virtually 0 to approximately 3 cm h‐1. The lowest Ksat values (<0.3 cm h‐1) occurred in or near the transitional horizons that were directly below the Bt horizons. Changes in the volume of pores within or between mineral grains (termed inter/intraparticle pores) with depth corresponded to changes in both Ksat and Kunsat. In the transitional horizons, the inter/intraparticle pores were plugged with clay and this caused the horizons to have low K values. In situ measurements of Ksat with depth were the most accurate technique to use for identifying transitional zones in the field. Examination of both the soil and rock structures in pits was also an acceptable technique. Texture and consistence were not considered reliable for pin‐pointing transitional horizons.
Water Distribution in Soil under Ridge‐Till and No‐Till Corn
Authors: Waddell J. T. , Weil R. R. 
Published: July 2010

AbstractNo‐till (NT) reduces runoff, but increases infiltration and macropore flow, compared with conventional tillage (CT). Because it controls traffic and creates a unique surface microtopography, we hypothesized that ridge tillage (RT) would alter water entry and distribution in the soil profile. Therefore, a field study using 5‐yr‐old NT and RT plots was conducted on a Monmouth fine sandy loam (fine‐loamy, mixed, mesic Typic Hapludult) in Maryland. Corn (Zea mays L.) plots in a corn‐soybean [Glycine max (L.) Merr.] rotation were studied for 2 yr. Soil sorptivity, determined by runoff from simulated rain, was 2.83 cm h‐1/2 on NT and 1.33 cm h‐1/2 on RT. Runoff began 26.3 min after rain began on NT vs. 7.2 min on RT. Also, NT retained more soil water than RT plots in 1991, when June to October rainfall was 290 mm. With 440 mm of June to October rainfall in 1992, depletion of water by corn was greater in NT than RT. The corn canopy funneled rain toward the corn row, largely offsetting interridge runoff in RT while the corn was present. Therefore the horizontal distribution of water was relatively uniform in RT soil, but water was concentrated in the corn rows in NT. After corn harvest in 1991, a dry period produced an upward water potential gradient in RT from − 18 kPa in the furrow to − 35 kPa on the ridgetops, but a downward gradient in NT from − 10 kPa near the surface to ‐25 kPa at 80 cm deep. The results suggest that RT may decrease water infiltration in the crop row, especially after harvest, compared with NT.
Soil Temperature, Water Content, and Barley Development of Level vs. Ridged Subarctic Seedbeds
Authors: Sharratt B. S. 
Published: July 2010

AbstractRidge tillage may promote early‐season warming of soils in subarctic regions and thereby optimize the plant growing environment. This study was conducted to assess soil temperature and water content, along with barley (Hordeum vulgare L.) development, on a level vs. ridged Pergelic Cryaquept at Fairbanks, AK. Ridges were oriented north‐south, east‐west, northeast‐southwest, and northwest‐southeast. Seed zone soil temperature and water content were measured, the former by thermocouples, at the ridge peak and furrow as well as on ridge slopes where barley was grown during the 1989 through 1991 growing seasons. Barley grown on the level surface and on southerly ridge aspects produced at least 25 g m‐1 more grain and 20 g m‐1 more straw than barley grown on northerly aspects. The vegetative developmental rate was 0.03 leaves d‐1 faster on southern ridge aspects or the level surface than on northern aspects, owing to 2°C higher temperatures of soil with a southerly or level exposure. Soil water content on northern ridge aspects was occasionally 0.05 m3 m‐3 higher than on southern aspects in the early growing season (<60 d after planting), but 0.04 m3 m‐3 lower than on the level soil surface in the late growing season (>60 d after planting). In the subarctic, the plant growing environment is as favorable on a level soil surface as on a south‐facing ridge aspect, owing to nearly equal early‐season soil temperatures and higher soil water content in the late season.
Specific‐Gravity Effects on Fertilizer Leaching from Surface Sources to Shallow Water Tables
Authors: Bonczek J. L. , McNeal B. L. 
Published: July 2010

AbstractSubirrigated sands with surface‐applied fertilizer bands are susceptible to considerable gravity‐induced convection of fertilizer salts whenever the water table approaches within 30 to 45 cm of the soil surface and induces rapid fertilizer dissolution. Laboratory studies have been conducted on two sands from Manatee County in the vegetable and citrus production region along central Florida's Gulf Coast. Peak saturated‐zone electrical conductivity (EC) values of 14 and 9 dS m−1 were attained within 3 to 5 d at the 60‐cm depth for columns of local sand having a water table maintained 2.5 and 22.5 cm below the soil surface, respectively. Such movement is far too rapid to be ascribed to reasonable diffusional or traditional convective‐flow effects, and is instead attributed to gravity‐induced convective flow, or fertilizer “dropout”. Sectioned‐column studies demonstrated near‐surface EC values of 25 to 35 and 70 to 90 dS m−1 for water tables maintained at the 15‐ and 45‐cm depths, respectively. These same columns evidenced solute‐pulse movement to the 8‐ to 10‐cm depth and the 15‐ to 20‐cm depth after 6 and 24 h, respectively, for water tables maintained at the 45‐cm depth. Lower hydraulic conductivity, quite possibly as a result of increased soil organic matter content for these otherwise virtually identical fine sands, moderated such effects somewhat. Implications are discussed with respect to early‐season fertilizer management in vegetable production regions of the southeastern Coastal Plain.
Solution For Heat Flow in Soil with a Heat Source at a Fixed Depth
Authors: Álvarez J. , Sobrón F. , Bolado S. 
Published: July 2010

AbstractWe developed a computationally efficient model for estimating the transient soil temperature distributions resulting from a heat source at a fixed depth beneath a greenhouse. The model was developed for use as a submodel of the air‐soil systems in greenhouses where the soil is used as a heat storage medium, with a network of buried pipes acting as a heat exchanger. The model assumes soil thermal properties are spatially and temporally constant and that energy transfer between the greenhouse and soil is primarily a result of net radiation and sensible heat transfer. First‐order energy transfer terms are also used to account for lateral energy exchanges with the surrounding soil and the heat source is included as a plane at a fixed depth. This was achieved by obtaining a Green's function solution in the Laplace domain and performing a numerical inversion with a fast Fourier‐transform algorithm, which requires very little computational time. Model parameters are optimized using a Simplex algorithm during a 3‐d simulation to show the ability of the method to describe the greenhouse soil temperature. This method provides a reasonable description of the heat flux under these conditions.
Soil Texture and Residue Addition Effects on Soil Phosphorus Transformations
Authors: Huffman S. A. , Cole C. V. , Scott N. A. 
Published: July 2010

AbstractThe effect of soil texture on P transformation and the extent and timing of crop residue decomposition affects both P availability and the fate of the P added in the residue. Our objectives were to examine P transformation in sand, sandy loam, and loam soils during surface or incorporated wheat (Triticum aestivum L.) straw decomposition with and without N and P addition. Packed soil cores (4.8 cm diameter by 2.5 cm deep) were incubated in the dark for 10, 30, 60, and 90 d at 25°C and −0.033 MPa initial soil water pressure. We determined CO2 respiration, labile inorganic P (Pi), labile organic P (Po), microbial P, NaOH‐extractable Pi and Po, and HCl‐extractable Pi. Soil texture had a greater effect on P transformation than did residue placement. Microbial P was greatest at 10 d and was 13.0, 9.8, and 6.5 mg kg−1 for the loam, sandy loam, and sand, respectively. Labile Pi was lowest at 10 d and was 22.9, 18.0, and 11.5 mg kg−1 for the loam, sandy loam, and sand, respectively. More of the nutrient P added remained as labile Pi when the residue was surface applied. Residue placement did not affect microbial P, indicating that the effect of placement was indirect. Phosphorus transformations were closely linked to microbial activity and C dynamics.
Stability Constants of the Fungal Siderophore Rhizoferrin with Various Microelements and Calcium
Authors: Shenker M. , Chen Y. , Hadar Y. 
Published: July 2010

AbstractStability constants of metal‐ligand complexes determine their speciation in solution at equilibrium. Therefore, stability constants of siderophore‐metal complexes are of crucial importance in studies of their efficiency as Fe mediators. In this study, potentiometric titrations were used to determine protonation and stability constants of Fe3+, Fe2+, Cu2+, Ca2+, and Zn2+ with rhizoferrin, a siderophore produced by Rhizopus arrhizus, which has been shown in previous studies to be an effective carrier of Fe to plants. Rhizoferrin was found to be a specific Fe3+ chelator but with a stability constant lower than most microbial siderophores. The ferric complex of rhizoferrin is anionic throughout the pH range prevailing in soils, and therefore, it is expected to be mobile in the rhizosphere. The following log Kapp values at 25°C, pH 7.0, and 0.1 M ionic strength were determined: 19.1, 7.5, 6.2, 6.0, and 4.4 for Fe3+, Fe2+, Cu2+, Ca2+, and Zn2+, respectively. The apparent stability constant (Kapp) value for the ferric complex of rhizoferrin suggests that ligand exchange with mugineic acid is the mechanism facilitating the efficiency of rhizoferrin as an Fe carrier to graminaceous plants.
Phosphorus Availability from Phosphate Rock as Enhanced by Water‐Soluble Phosphorus
Authors: Chien S. H. , Menon R. G. , Billingham K. S. 
Published: July 2010

AbstractQuantitative estimation of the enhancement effect of water‐soluble P on P availability from phosphate rock (PR) has not been reported. The objective of this study was to use radioactive 32P as a tracer to distinguish P availability from soil, PR, and TSP so that P uptake by crops from PR in the presence of TSP could be estimated. Three sets of 4‐kg soil samples of an acid Hartsells silt loam (fine‐loamy, siliceous, thermic Typic Hapludult, pH 4.8) were mixed with the following treatments: (i) 32P solution and central Florida PR (CFPR), (ii) 32P‐tagged TSP, and (iii) 32P‐tagged TSP and CFPR at a P ratio of 50:50. The rates of P applied were 0, 12.5, 25, 50, 100, and 200 mg P kg−1. For treatment (iii), an additional rate of 400 mg P kg−1 was also prepared. Maize (Zea mays L.) and cowpea (Vigna unguiculata [L.] Walp. ssp. unguiculata) were planted and harvested at 42 d after planting for maize and 45 d for cowpea. The effectiveness of P sources in terms of increasing dry‐matter yield and P uptake followed the order of TSP >‐ (CFPR + TSP) > CFPR for maize and TSP = (CFPR + TSP) > CFPR for cowpea. Phosphorus uptake from CFPR in the presence of TSP was higher than P uptake from CFPR applied alone, indicating an enhancement effect of TSP on the effectiveness of CFPR. The increase in P uptake from CFPR due to TSP influence, across all the PR rates applied, was 3.48 mg P pot−1 for maize and 1.38 mg P pot−1 for cowpea. With respect to P uptake from CFPR applied alone, the corresponding relative increase in P uptake from CFPR due to TSP influence was 165% for maize and 72% for cowpea.