bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Three Spectrophotometric Methods for Differentiating Mono‐ and Polynuclear Hydroxy‐Aluminum Complexes
Authors: Parker D. R. , Zelazny L. W. , Kinraide T. B. 
Published: July 2010

AbstractIncreasing interest in the relationships between aluminum (Al) speciation and biological toxicity has created a need for accurate methods for speciating aqueous Al. Polynuclear hydroxy‐Al complexes are generally viewed as metastable species, and are thus more amenable to empirical than to computational approaches to speciation. The objectives of this study were to evaluate and compare the ferron (8‐hydroxy‐7‐iodo‐5‐quinoline‐sulfonic acid), aluminon (aurintricarboxylic acid, triammonium salt), and 8‐hydroxyquinoline methods for their ability to differentiate mono‐ and polynuclear Al in solutions typical of those used in related phytotoxicity studies. Test solutions were 20 µM in AlCl3, 0.4 mM in CaCl2 or 40 mM in NaCl, and had basicities (molar OH/Al ratios) ranging from −1 to 2.25. Reactions between test solutions and ferron or aluminon were kinetically modeled as two parallel irreversible reactions to yield estimates of the mononuclear fraction, fm. The reaction of 8‐hydroxyquinoline with mononuclear Al was essentially instantaneous, and use of an arbitrary cutoff was unavoidable. Estimates of fm were in the order 8‐hydroxyquinoline > ferron > aluminon at low basicities, while at a basicity of 2.25 the general order was aluminon ≥ 8‐hydroxyquinoline > ferron. Increasing ionic strength of test solutions increased estimates of fm by all methods. Significant quantities of polynuclear Al were detected even in solutions without added base or with slight acidification. Aging solutions up to 32 d resulated in decreased estimates of fm using aluminon, but estimates using ferron and 8‐hydroxyquinoline were only minimally affected. All three methods yield results of adequate precision for most purposes, although the ferron procedure is somewhat less sensitive than the other two. Additional studies using ferron demonstrated its utility for characterizing the nonmononuclear Al fraction using kinetic analyses. Ferron may be the preferred method based on its simplicity, level of precision, and moderate reaction rate with Al.
Boron and Silicon Adsorption on an Aluminum Oxide
Authors: Goldberg Sabine , Glaubig R. A. 
Published: July 2010

AbstractBoron and Si adsorption on the Al oxide, alon (δ‐Al2O3), were investigated under changing conditions of pH, total solution anion concentration, reaction time, and order of anion addition. Boron adsorption increased at low pH, exhibited a peak near pH 8, and decreased at high pH. The constant capacitance model was successfully used to describe B adsorption over the pH range 5 to 9 and at initial B concentrations ranging from 0.185 to 1.85 mol m−3 using only one adjustable parameter, the B surface complexation constant. Silicon adsorption was much greater than B adsorption and exhibited a broad maximum extending from pH 6 to 10. Simultaneous B and Si adsorption produced a small, significant reduction in B adsorption but had no effect on Si adsorption, indicating that some of the sorption sites showed anion preference. The magnitudes of the adsorption maxima for B and Si remained essentially constant for total reaction times ranging from 10 min to 24 d. The Al oxide was very soluble, solutions were supersaturated with respect to gibbsite after 10 min at pH 4.6 to 5.7. We therefore recommend short reaction times (<2 h) for the study of adsorption reactions on δ‐Al2O3 and amorphous Al oxide.
Previous Sludge Addition Effects on Nitrogen Mineralization in Freshly Amended Soil
Authors: Lindemann W. C. , Connell G. , Urquhart N. S. 
Published: July 2010

AbstractAn experiment was conducted to determine the effects of previous sludge additions on N mineralization in a freshly amended soil. A secondary objective was to further delineate statistical models of N mineralization potential (No) and the mineralization rate constants k and h. The Glendale clay soil (fine‐silty, mixed thermic, Typic Torrifluvents), with either no previous sludge amendment or sludge applied at the rate of 67.3 Mg ha−1 in 1982 or 1983 in the field, was freshly amended with 30 g kg−1 of gamma irradiated, dried, anaerobically digested sewage sludge in 1985. Triplicate samples of each soil (unamended, amended in 1982, and amended in 1983) and each sludge treatment (no amendment and freshly amended) were incubated aerobically for 16 wk at 0.01‐MPa moisture potential and 35 °C. Periodically the soils were leached with 0.01 M CaCl2, and the leachate was analyzed for inorganic and organic N. Previous sludge amendment had no effect on the mineralization of resh sludge. Soils previously amended in 1982 and 1983 leached 56 to 60 mg kg−1 more NO‐3 + NO‐2 than unamended or freshly amended soils never amended with sludge. Total organic N mineralization averaged 65.4% and was independent of soil amendment history or fresh sludge amendment. Values of No, k, and h were estimated by nonlinear least squares for several nonlinear models. The best fit of the data resulted from modeling N mineralization as the sum of an exponential equation (of the rapidly decaying organic N fraction) and a constant (of the slowly decaying organic N fraction). Mineralization curves failed to flatten after 16 wk, suggesting that the experiment should have run longer before a two‐exponential equation would have satisfactorily explained the data.
Reductions in Exchangeable Magnesium with Liming of Acid Ohio Soils
Authors: Myers J. A. , McLean E. O. , Bigham J. M. 
Published: July 2010

AbstractReductions in exchangeable Mg with liming have frequently been reported in acid soils. It has been suggested that such reductions are due to an interaction between exchangeable Mg and soil Al; however, the form(s) of Al responsible for the interaction has not been adequately defined. Consequently, the objectives of this study were to fractionate the Al occurring in a series of acid Ohio soils and to determine if a relationship between Al and Mg could be defined in order to predict those soils where reductions in exchangeable Mg with liming may pose a potential problem for plant nutrition. Laboratory treatments were applied to seven soil materials in a 4 × 2 factorial, with four lime (no lime, pH 5, pH 6, pH7) and two Mg levels (0 and 25% of the cation exchange capacity, CEC). Losses in exchangeable Mg were regressed against Al solubilized by six extractants commonly used for Al fractionation, including KCl, NH4‐acetate, CuCl2, Na‐citrate‐dithionite, NH4‐oxalate, and Na‐pyrophosphate. Reductions in exchangeable Mg with liming were observed over a range of equilibrium pH values; however, the effect was clearly enhanced by increasing the soil pH to neutrality. Addition of supplemental Mg to the soils increased the absolute amount of exchangeable Mg lost with liming but had little effect on the nature of the response. Decreases in exchangeable Mg in those soils limed to near neutrality ranged from 17 to 34% of that initially present. The reduction in exchangeable Mg was positively correlated with several soil Al fractions including exchangeable, organically chelated, and poorly crystallized inorganic species; however, exchangeable Al produced the best correlation supporting the hypothesis that Mg “fixation” is due to the occlusion or coprecipitation of Mg with Al upon liming.
Effect of Phosphorus Level on Extractable Micronutrients and Their Distribution Among Soil Fractions
Authors: Shuman L. M. 
Published: July 2010

AbstractReduced tillage can cause high P levels at the soil surface which may influence soil properties so as to redistribute micronutrient metals among soil fractions and alter their plant availability. The objective was to determine the effect of P levels on the distribution of Mn, Cu, Fe, and Zn among soil fractions and on their extractability by commonly used soil extractants. Eight topsoils were treated with 0, 30 and 60 mg P kg−1 soil and none or one level of a blend of Mn, Cu, and Zn. After 22 wks, the soils were sequentially extracted to separate the exchangeable, organic, Mn oxide, amorphous Fe oxide, crystalline Fe oxide, and residual fractions. Mehlich‐1, Mehlich‐3, and DTPA (diethylenetriamine‐pentaacetic acid) extractable metals and Mehlich‐3 P were also determined. Increasing P moved Mn from the less‐soluble fractions (crystalline Fe oxide and residual) to the intermediately‐soluble fractions (Mn oxide and amorphous Fe oxide) and had little effect on the plant‐available fractions (exchangeable and organic). Copper moved to the exchangeable from the residual fraction for the fine‐textured soils. Zinc moved from the Mn oxide and crystalline Fe oxide fractions to the exchangeable fraction for all soils. Added Cu and Zn were evident in the more plant‐available fractions for most soils. Increased P increased extractable Mn and Fe for Mehlich‐1 and −3 and DTPA. Phosphorus treatments increased soil pH probably because of reactions with Fe and Al oxides producing hydroxyl ions. However, initial reactions may have lowered soil pH causing metals to be more soluble.
Acid‐Subsoil Amelioration: I. A Comparison of Several Mechanical Procedures
Authors: Farina M. P. W. , Channon P. 
Published: July 2010

AbstractIn many high potential cropping areas, particularly of the tropics and subtropics, crop exploitation of subsoil moisture reserves is prevented or severely curtailed by high levels of exchangeable Al. Since the effects of surface incorporated lime on subsoil acidity are minimal in most highly weathered soils, specialized mechanical and/or chemical procedures are required to overcome the problem. This work was conducted in order to assess the practicalities of mechanical profile modification and to compare the efficacy of several possible procedures. In a field experiment with maize (Zea mays L.) on a strongly acidic Plinthic Paleudult conventional moldboard incorporation of lime was compared to lime incorporation using a deep moldboard plow, the Wye‐double‐digger, a modified subsoiler capable of incorporating vertical bands of ameliorated topsoil to depths of 0.7 m, and a deep limer designed to ameliorate vertical bands of soil to a similar depth. All the procedures tested proved superior to conventional liming, the average response to profile modification ranging from over 1 400 kg ha 1 in a season in which severe moisture stress was experienced to approximately 400 kg ha−1 in an exceptionally high rainfall season. Yield responses were related to increases in rooting volume and to changes in root configuration. Segmental liming proved as effective as deep plowing or double digging.
Acid‐Subsoil Amelioration: II. Gypsum Effects on Growth and Subsoil Chemical Properties
Authors: Farina M. P. W. , Channon P. 
Published: July 2010

AbstractIn many highly weathered soils crop exploitation of subsoil moisture reserves is severely curtailed by toxic levels of Al. Since vertical movement of lime is usually extremely slow in such soils, specialized mechanical and/or chemical procedures are required to overcome the problem. A field experiment with maize (Zea mays L.) on a strongly acidic Plinthic Paleudult examined the effects of surface‐incorporated gypsum on yield, root development, and profile chemical properties for four cropping seasons. The effects of gypsum (10 Mg ha−1) were time dependent, but by the fourth season had resulted in a cumulative grain yield gain of 3.4 Mg ha−1. Progressive depressions in the level of exchangeable Al were accompanied by increases in subsoil Ca, Mg, and SO4‐S. Water pH increased markedly in the zone of maximum SO4‐sorption/precipitation, but pH determined in KCl remained unchanged. By the fourth season the effects of gypsum on subsoil root development were striking. These results indicate that surface incorporation of gypsum is an economically viable approach to subsoil amelioration on soils such as that studied here.
Soil Compaction and its Effect on Alfalfa in Zone Production Systems1
Authors: Meek B. D. , Rechel E. A. , Carter L. M. , DeTar W. R. 
Published: July 2010

AbstractAlfalfa (Medicago sativa L.) was grown under two zone production systems (no harvest traffic) (i) preplant compaction and (ii) no preplant compaction and compared to two systems where traffic was applied (i) to 100% of the area during each harvest and (ii) to lanes simulating the traffic a grower would apply during harvest. The experiment was done in a semiarid area under irrigation on a Wasco sandy loam (coarse‐loamy, mixed, nonacid, thermic Xeric Torriorthent), which is easily compacted. Without traffic the soil settled to a bulk density of 1.6 to 1.70 Mg m−3. Traffic increased the bulk density to the 1.8 to 1.9 Mg m−3 range. Increases in bulk density at the 0.05‐ and 0.15‐m depths occurred only during the first five passes of traffic, but 10 passes were required to reach a stable bulk density at depths of 0.25 to 0.5 m. Traffic similar to what a grower would apply reduced yields by 10% compared with no traffic. Compacting 100% of the soil surface after each harvest reduced yields 17% compared with no traffic.
A Method for Measuring Hydraulic Properties of Brittle Soil Horizons
Authors: Vroon H. R. J. , Dekker L. W. , Hendrickx J. M. H. 
Published: July 2010

AbstractA method is presented for measuring hydraulic properties of undisturbed samples of brittle soil horizons oriented vertically or horizontally. A soil pedestal is carved out in situ and covered with a mixture of nitrocellulose lacquer and thinner. The saturated hydraulic conductivity is measured by infiltrating water into the exposed upper surface and by collecting it below the exposed lower surface of the pedestal. In brittle soil horizons, the method yielded more representative conductivity values than the method that uses steel cylinders for taking “undisturbed” soil cores. Measurements of water retention and hydraulic conductivities showed that the latter method often disturbed the structure of the sample. Therefore, artificially high conductivity values were obtained. The method presented allows measurement of vertical and horizontal conductivities and soil‐water retention using the same sample. The method is simple and allows adjusting the sample volume to the phenomenon under study. Therefore, the method facilitates the study of hydraulic properties of brittle horizons, such as sandy humus hardpans.
Fluorescence Quenching and Copper Complexation by a Chestnut Leaf Litter Extract: Spectroscopic Evidence
Authors: Sposito Garrison , Holtzclaw Kenneth M. , Senesi Nicola 
Published: July 2010

AbstractFluorescence quenching on addition of Cu(II) to aqueous solutions of chestnut (Castanea sativa L.) leaf litter extract (LLE) has been interpreted previously in terms of Cu complexation by LLE organic ligands. In order to provide direct evidence for the existence of these complexes, as well as information about their coordination structures, infrared (IR) and electron spin resonance (ESR) spectroscopy were applied to investigate Cu/LLE mixtures that showed increasing fluorescence quenching with increasing pH. The Cu/LLE mixtures were prepared with approximately equimolar concentrations of Cu and LLE binding sites (200 mmol m−3) at pH values in the range 4 to 7. The IR spectra indicated the existence of Cu complexes involving carboxylate groups, even at pH 4. The more sensitive ESR spectra showed that Cu(II) could displace Fe(III) and Mn(II) from LLE binding sites, and that inner‐sphere complexes between Cu and LLE ligands were formed. These complexes involved carboxylate ions and H2O molecules at pH < 6, and both O‐ and N‐containing ligands at pH 6 and 7. These results confirmed the hypothesis that fluorescence quenching is associated with strong Cu complexation by organic ligands in the LLE.
Competitiveness of Selected Bradyrhizobium japonicum Strains in Midwestern USA Soils
Authors: Klubek B. P. , Hendrickson L. L. , Zablotowicz R. M. , Skwara J. E. , Varsa E. C. , Smith S. , Islieb T. G. , Maya Jaime , Valdes Maria , Dazzo F. B. , Todd R. L. , Walgenback D. D. 
Published: July 2010

AbstractThe competitiveness of 19 selected Bradyrhizobium japonicum strains in the midwestern USA was evaluated in field studies during 1984 and 1985. Of the 11 selected strains evaluated in 1984, a range in nodule occupancy of 0.3 to 15.7% was observed across three locations in Illinois and Wisconsin. During the second year of the study, 7 of 12 strains showed nodule occupancy averaging between 14.8 to 26.6% for eight locations in Illinois, Michigan, South Dakota, and Wisconsin. Strain An‐11 exhibited an average nodule occupancy of 15.7% in 1984 and 26.6% in 1985 which was significantly greater than any of the other 18 strains tested. Estimates of biologically‐fixed N via non‐nodulating isolines of soybean (Glycine max L.) showed a significant difference between one inoculum treatment (strain An‐14) and the noninoculated control for only one location (Plainfield, WI) during the second year of the study. No significant differences in grain yield were observed in either year of the study. The data suggests that selected strains of B. japonicum can be more successfully introduced into midwestern USA soils if they are adapted for the soils and cultivars in that geographic region.
Direct Measurement of Dinitrogen and Nitrous Oxide Flux in Flooded Rice Fields
Authors: Buresh R. J. , Austin E. R. 
Published: July 2010

AbstractA direct 15N method was used to measure N2 and N2O flux in flooded rice (Oryza sativa L.) fields. The method involved application of a highly 15N‐enriched source to a 0.4‐m by 0.4‐m microplot, collection of evolved N2 and N2O in a chamber placed over the flood‐water, removal of NH3 from the air sample, conversion of some (N2 + N2O)‐N in the air sample to NH+4‐N, and determination of 15N content with a mass spectrometer. The flux of (N2 + N2O)‐15N was measured for 17 d following urea application by three methods, each replicated four times, on a Vertic Tropaquept. In all cases, the (N2 + N2O)‐15N flux was much smaller than total gaseous 15N loss as estimated from unaccounted for 15N in the 15N balance after 18 d. The (N2 + N2O)‐15N flux and total 15N loss were 1.1 and 40%, respectively, following basal broadcast and incorporation of 58 kg urea‐N ha−1 with 2‐cm standing water; they decreased to 0.2 and 26%, respectively, when the urea basal incorporation was without standing water. The (N2 + N2O)‐15N flux and total 15N loss were 0.5 and 46%, respectively, following application of 44 kg urea‐N ha−1 to 50‐mm floodwater at 10 d after transplanting. The methodology could detect a flux of 10 g N ha−1 d−1 from the added 59 to 64 atom % 15N‐labeled urea. Additional studies with 15N‐labeled NO‐3 evaluated the possibility that the low (N2 + N2O)‐15N flux was due to incomplete recovery of N2 and N2O formed from added fertilizer. Direct recovery of (N2 + N2O)‐15N following addition of labeled NO‐3 ranged from 41 to 73% of the total 15N loss. No 15N was lost by leaching or runoff, and dissolved N2O in the floodwater calculated from published solubility data was less than 1% of the added 15N.
Irrigated Corn Response to Soil‐Test Indices and Fertilizer Nitrogen, Phosphorous, Potassium, and Magnesium
Authors: Obreza T. A. , Rhoads F. M. 
Published: July 2010

AbstractImproved soil‐water management techniques have made irrigated corn (Zea mays L.) yields of more than 12.5 Mg ha−1 possible in the southeastern USA. Data relating fertilizer rates and soil test indices to grain yield under intensive water management are needed to maximize fertilizer use efficiency. The objective of this study was to generate fertility index‐yield response data from which critical levels of Mehlich 1 soil test P, K, and Mg could be calculated. Irrigated corn was grown at Quincy, FL during 1980 and 1981. Nitrogen was applied at 168, 336, and 504 kg ha−1, P at 0, 29, 59, and 118 kg ha−1, K at 0, 209, and 418 kg ha−1, and Mg at 0, 67, and 134 kg ha−1 in a total of 11 treatments. Indices of available nutrients were measured via the Mehlich 1 soil test prior to each season. For both years, a minimum application of 168 kg ha−1 of N, 29 kg ha−1 of P, and 0 kg ha−1 of Mg was required for maximum grain yield, which averaged 11.2 Mg ha−1. For K, maximum yield occurred with minimum applications of 209 and 0 kg ha−1 in 1980 and 1981, respectively. Calculated critical Mehlich 1 soil test levels were 9, 45, and 33 mg kg−1 for P, K, and Mg, respectively. Comparison of our results with current soil test rating categories and corresponding recommended fertilizer rates indicated that maximum corn yield was obtained with a P fertilizer rate which was 50 kg ha−1 lower than the recommended rate.
Mineralogy and Incipient Pedogenesis of Entisols in Anorthosite Terrane of the San Gabriel Mountains, California
Authors: Graham R. C. , Herbert B. E. , Ervin J. O. 
Published: July 2010

AbstractEntisols on anorthosite and associated mafic dikes in the San Gabriel Mountains were examined to determine the influence of contrasting parent materials on soil mineralogy and incipient pedogenesis. Soils are shallow Xerorthents on chaparral‐covered slopes of 50 to 65% gradient. The anorthosite is composed almost entirely of plagioclase and laumontite, a hydrothermally produced Ca‐rich zeolite. Hornblende is the major constituent of the mafic rock, while plagioclase and laumontite are much less abundant. Soil properties are strongly influenced by the parent material. Soils on the aphanitic mafic rock have much higher silt contents than those on the coarsegrained anorthosite. Calcium dominates the exchange of soils on both lithologies, but exchangeable Mg values are higher in the mafic soil than in the soil on anorthosite. A soil pH of up to one unit higher in the anorthosite‐derived soil is probably the result of the hydrolysis reaction in which the abundant, easily weathered plagioclase and zeolite weather to kaolin. Poorly crystalline kaolinite and halloysite are the dominant clay minerals in the anorthosite‐derived soil. The soil developed from mafic rock contains a large proportion of well‐crystallized trioctahedral smectite in addition to kaolin. The smectite is inherited from the mafic rock which has been somewhat hydrothermally altered. X‐ray diffraction and optical analysis of the parent rock and soil fractions coarser than clay also detected smectite and averted its misinterpretation as pedogenic. Cation exchange capacities (CEC) that are excessively high for the amount and kinds of clay present are apparently caused by CEC contributions of smectite and zeolite in the silt and sand fractions. Slight weathering of hornblende is responsible for the citrate‐bicarbonate‐dithionite‐extractable Fe, which is generally low, but is highest in the mafic soil and increases in A and AC horizons. The A and AC horizons of all soils exist in a quasi‐stable colluvial mantle and have mineral components from both lithologic sources, whereas the mineralogy of C and Cr horizons reflect only the underlying rock. Denudation rates on the steep, chaparral‐covered slopes indicate that no part of the soils, including the Cr horizons, can be older than 400 yr. Pedogenesis is inhibited by high erosion rates on this steep terrain.
Soil Cohesion as Affected by Freezing, Water Content, Time and Tillage
Authors: Bullock M. S. , Nelson S. D. , Kemper W. D. 
Published: July 2010

AbstractThis study was developed to determine whether there are substantial annual changes in soil cohesion and to identify major factors causing those changes. Aggregate stability was measured throughout the year on soils in Utah and Idaho using wet sieving techniques. Stability generally increased during spring and summer months. Major decreases of cohesion, found when minimum daily air temperatures fell to or below 0 °C during winter and early spring months, were attributed to pressures and associated shearing forces caused by freezing at high water contents. Equivalent disruption occurred when confined soils were frozen in controlled laboratory studies. Disruption also increased as water content at the time of freezing increased for all soils studied. Disruption of soil by rototilling and compaction significantly decreased soil cohesion.