bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solution Sulfate Chemistry in Three Sulfur‐Retentive Hydrandepts
Authors: Wolt J. D. , Hue N. V. , Fox R. L. 
Published: July 2010

AbstractHighly S‐retentive Hydrandepts frequently contain large quantities (> 200 mmol kg‐1) of sorbed S while exhibiting low S intensities in soil solution. Solution‐solid phase S relations for three representative Hydrandepts from Hawaii were investigated in terms of the nature of sorption isotherms and the role of basic Al hydroxysulfate precipitation as a mechanism for S retention. Sorption data were fit to linear, Langmuir, and multisite Langmuir isotherms using a modeling routine that performed parameter estimates and model optimization using weighted nonlinear fitting. Best‐fit models indicated sorption data were adequately described by Langmuir isotherms. Total P‐extractable SO4‐S increased markedly at depths > 45 cm and tended to decline at depths > 120 cm. Extractable SO4‐S was strongly regressed on gravimetric moisture content, a relative indicator of reactive surface for these thixotropic soils. Soil solution SO4‐S concentrations were consistent with alunite or basaluminite solubility when gibbsite controlled solution Al3+.
Evaluation of Direct/Delayed Response Project Soil Sampling Classes: Northeastern United States
Authors: Adams M. B. , Turner R.S. , Schmoyer D. D. 
Published: July 2010

AbstractThe Direct/Delayed Response Project (DDRP) identified approximately 600 soils on 145 watersheds in the northeastern USA. Soils were assembled into 38 sampling classes, based on soil characteristics thought to influence surface water chemistry. Multivariate analysis techniques were used to evaluate the utility of the sampling classes. Hydrologic and chemical properties of soils were determined to be the most important for discriminating among the sampling classes. Although sampling class was a statistically significant effect for most soil chemistry variables, only a few sampling classes were particularly distinct (some Entisols, Histosols, and Inceptisols with high base saturation). For most variables, within‐sampling‐class variability was less than or equal to between‐class variability, although this was not true for all of the characteristics evaluated. No better classification approaches were identified in this analysis. The DDRP sampling classes provide a means for grouping soils for efficiency in regional soil sampling, characterization, and aggregation to mapped areas.
Proton Effects on Quaternary Cation Exchange and Flocculation of Silver Hill Illite
Authors: Thellier Catherine , Sposito Garrison , Holtzclaw Kenneth M. 
Published: July 2010

AbstractThe investigation of quaternary cation exchange and flocculation in dilute suspensions of illite with mixed Na‐K‐Ca‐Mg perchlorate solutions was extended to consider the effect of aqueous protons. The exchange reactions and flocculation of Silver Hill illite at inial pH (pHi) = 6 or 8, three total perchlorate concentrations (9, 5, or 2 molc m−3), and varying initial Na/Ca or Na/Mg ratios in the aqueous solution phase were studied. It was found that pHi had little or no effect on exchangeable cation selectivity or total adsorbed metal charge. The degree of flocculation, as described by the percentage light transmission through the illite suspensions, was found to be highly pHi dependent. The effect of pHi was greatest in the 5 molc m−3 perchlorate background, where, at an exchangeable bivalent charge fraction near 0.3, the suspension was almost completely flocculated at pHi = 6 but dispersed at pHi = 8. Overall, at a given exchangeable bivalent charge fraction, the illite suspensions became less flocculated, and showed greater sensitivity to exchangeable Ca vs. Mg, as pHi increased from 6 to 8. Changes in pHi thus produced colloidal effects just the inverse of changes in the total perchlorate concentration. Analysis of the pH dependence of the light‐transmission data suggested that the mechanism of illite flocculation was affected greatly by the adsorption‐desorption reactions of a small number of protons on the edge surfaces of suspended particles.
Soil Drying and Rewetting, or Freezing and Thawing, Affects Soil Solution Composition
Authors: Walworth J. L. 
Published: July 2010

AbstractAnalysis of soil solution is a useful tool for soil fertility characterization and environmental studies, yet little is known about the effects of soil storage and handling on the solution collected. A laboratory study was conducted to determine the effects of time of extraction and preextraction freezing and thawing, or drying, rewetting, and incubating on centrifugally collected soil solutions. The relationship between electrical conductivity (EC) and ionic strength (I) also was studied. Samples of Bt horizons of three Hapludults were centrifuged at 750 g and solutions were collected after 20, 60, 120, and 240 min. Solutions were collected from fresh soils and from soils that had been frozen and thawed, or air dried and rewetted to their original water content, and then incubated for various periods of time. Solutions were analyzed for EC, pH, NH4, Ca, K, Mg, Na, Cl, F, NO3, and SO4. Significant changes in soil solution composition were found as centrifugation time was varied, indicating the importance of this parameter in soil solution extractions. The relationship between EC and I was very close to those previously described; EC can provide a good estimate of I of soil solutions. Soil solution composition was substantially altered by preextraction drying‐rewetting or freezing‐thawing. Following incubation, the composition of soil solutions from rewetted soils did not approach that of fresh soils. Neither of the methods studied here provided a good means of storing soil samples prior to soil solution extraction.
Quantity‐Intensity Relationships of Soil Ammonia in Long‐Term Rotation Plots
Authors: Thompson T. L. , Blackmer A. M. 
Published: July 2010

AbstractReports of release of nonexchangeable NH+4 from soils under some conditions and reports that management practices can change the affinity of the exchange complex for NH+4 indicate a need to reevaluate the commonly accepted practice of determining exchangeable NH+4 to assess the availability of NH+4 to plants. To address this need, quantity‐intensity (Q/I) relationships were studied in soil samples from two Iowa soils, a Webster clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll) and a Galva silty clay loam (fine‐silty, mixed, mesic Typic Hapludoll) in long‐term experiments having various crop‐rotation and N‐fertilizer treatments. The observed Q/I relationships gave no evidence for release of nonexchangeable NH+4. Potassium‐exchangeable NH+4 concentrations were well correlated with measurements of labile NH+4 (r = 0.91, P < 0.01) and equilibrium activity ratios for NH+4 (r = 0.89, P < 0.01). No significant relationship was found between relative affinity of the exchange complex for NH+4 and organic C within each soil. Soil management practices influenced NH+4 availability as evaluated by KCl‐exchangeable NH+4 and Q/I parameters, but did not change the relative affinity of the exchange complex for NH+4. Overall, indexes of NH+4 availability based on determinations of K‐exchangeable NH+4 were similar to those derived from studies of Q/I relationships.
Leaching of Inorganic Phosphorus from Litter of Southern Pine Plantations
Authors: Polglase P. J. , Jokela E. J. , Comerford N. B. 
Published: July 2010

AbstractA study was conducted to quantify leachable nutrients in needles of the litter layer of intensively managed southern pine plantations. The study site used for sampling of litter was a 2 × 2 × 2 factorial (three replicates) of species (slash [Pinus elliottii Engelm. var elliottii] and loblolly [P. taeda L.] pines), weed control (with or without complete and sustained weed control) and fertilizer application (with or without annual applications of essential elements). Fresh, intact needles collected in September and December 1989 and in March 1990 were soaked in distilled water (4°C, pH 4.9) for 5 d and measured for pools of soluble inorganic and organic P and N. Of these nutrients, only inorganic P (Pi) was detected in leachates. About 5 and 15% of the total P content was leached from Oi horizon needles in nonfertilized and fertilized plots, respectively. Because fertilizer application also doubled the total P content of Oi horizon needles, direct leaching losses will be important only in plots amended by fertilizer. A 5‐d time‐course experiment demonstrated that Pi was continuously leached from Oi horizon needles of the combination treatment, whereas the small amounts of Pi available for leaching in the Oe1 and Oe2 horizon needles were extracted immediately. In fertilizer‐amended plots, at least, the Oi horizon provides the majority of potentially leachable Pi.
Infiltration Simulations among Five Hydraulic Property Models
Authors: Alessi Sam , Prunty Lyle , Schuh W.M. 
Published: July 2010

AbstractAnalytical functions are used within computer models to give continuous representation of discrete data obtained from measurement. Functionally different equations have been used for soil hydraulic properties without concern for their smoothing effect on the data or their relationship to the stability of the numerical algorithm. This study evaluates the effect of five different power‐function representations of the soil water‐retention function and corresponding poreinteraction hydraulic‐conductivity representations on numerical solutions of Richards' equation. The functions were curve‐fit to 46 data sets for Hecla loamy fine sand (sandy, mixed Aquic Haploboroll). Minimum, median, and maximum function parameters (Campbell's b coefficient and air entry) were used to identify data sets from which one‐dimensional finite‐difference infiltration simulations were conducted. The wetting‐front location varied 6.0 to 8.0 cm (T = 6 min) among models, whereas variation within a model due to soil‐series‐imposed parameter variability was slightly larger (5.5–8.5 cm). Infiltration amounts varied −27 to 12% from the average among models. The results quantify sources of error due to curve‐fitting soil waterretention data to analytical functions assuming pore‐interaction theory.
Coupled Diffusion of Exchangeable Cations in Soil
Authors: Rhue Dean 
Published: July 2010

AbstractAlthough coupling of transport processes in soil has been studied for some time using the principles of irreversible thermodynamics, its importance with respect to coupled diffusion of cations in soil has not yet been fully determined. The purpose of this study was to evaluate the importance of coupled diffusion of cations in a sandy soil in which the pH‐dependent charge from organic matter represented a major proportion of the total cation‐exchange capacity. The degree of coupling was evaluated by determining what effect counterdiffusion of exchangeable K and Ca had on the distribution of exchangeable Na when the latter was initially at a uniform concentration throughout the system. Coupling was evidenced by a Na flux that was counter to, and ranged from 16 to 28% as large as, the K flux. The simultaneous diffusion of Ca, K, and Na was modeled by assuming that the coupling resulted from a diffusion potential arising from the counterdiffusion of K and Ca. Intrinsic diffusion coefficients required in the model were estimated from conductance data. Predicted and measured cation concentrations showed a highly significant linear correlation, with predicted concentrations averaging 96% of measured concentrations for all three cations.
Significance of Soil Chemical Heterogeneity for Spatial Behavior of Cadmium in Field Soils
Authors: Boekhold Alexandra E. , Van der Zee Sjoerd E.A.T.M. 
Published: July 2010

AbstractTo investigate the spatial behavior of Cd in an arable field and to analyze its dependency on pH and organic carbon content (OC), soil was sampled on a 0.5‐ha field and analyzed for HNO3‐extractable Cd and Zn contents (CdT and ZnT, respectively), soluble Cd and Zn contents (Cds and Zns, respectively), pH, and OC. All parameters were spatially variable and anisotropic. Within the sampled area the measurements became independent of each other for OC, for CdT and ZnT in the east‐west direction, and for Cds in the north‐south direction at distances of 5 to 20 m. For the other variables and directions, no range was observed. Similarity between anisotropy of HNO3‐extractable heavy metal contents and OC, as well as between soluble contents and pH, suggested a functional (spatial) relationship between these parameters. Because the field was anisotropic, the spatial structure of the parameters was different from the spatial structure obtained from transect analysis in the same field. Correlation between Cd and Zn contents was high, both in soluble and in HNO3‐extractable form. No correlation was observed between HNO3‐extractable and soluble heavy metal contents. Soluble Cd and Zn were highly correlated with pH. A significant correlation was found between CdT and ZnT and pH, and between HNO3‐extractable contents and OC. Using a scaled sorption model, variability of pH and OC was explicitly accounted for when calculating Cds from HNO3‐extractable Cd contents. Predicted Cd concentrations in the soil solution correlated well (r = 0.87) with measured Cd concentrations, whereas prediction when homogeneity of the sorption parameters is assumed yielded no significant correlation. Apparently, pH and organic‐matter content are the most important soil parameters that regulate Cd sorption in this soil.
Landscape‐Scale Variations in Denitrification
Authors: Pennock D. J. , van Kessel C. , Farrell R. E. , Sutherland R. A. 
Published: July 2010

AbstractDenitrification from agricultural ecosystems is regarded as a major contributor to atmospheric N levels, but the actual rates of denitrification and the controls on these rates remain poorly understood. This study was conducted to examine landscape‐scale patterns of denitrification and the soil properties that control these patterns. A 110 by 110 m sampling grid was established in an irrigated field in an aridic Boroll (Brown Chernozemic) soil in southern Saskatchewan. The measured soil properties (denitrification rate, respiration rate, volumetric water content, bulk density, soluble organic and inorganic C, total and mineral N, in situ pH, and in situ redox potential) were correlated to the derived landform elements at the site to determine landscapescale patterns and relationships. The soil properties occurred in one of three spatial patterns: (i) a random pattern for mineral N; (ii) a diagonal pattern for pH, soluble organic and inorganic C, and total N; and (iii) a depression‐centered pattern for denitrification, bulk density, moisture, respiration, and redox potential. Denitrification activity displayed a distinct landscape‐scale pattern and statistically distinct rates of denitrification were associated with the different landform elements: rates were lowest in the shoulder elements, intermediate in the footslope and level‐convex elements, and highest in the level‐concave elements. Hot spots of denitrification activity, i.e., sampling sites with denitrification rates identified statistically as outliers, were all associated with the level elements and, predominantly, the level‐concave elements. For the data set as a whole, denitrification was most highly correlated with volumetric water content (rs = 0.448**) and soil redox potential (rs = −0.335**). In the level landform elements, volumetric water content was the soil variable most highly correlated with denitrification; in the shoulder and footslope elements, respiration and bulk density, respectively, were the soil variables most highly correlated with denitrification. These data indicate that (i) topography has a strong influence over in situ denitrification, (ii) different controls are at work in the various landform elements, and (iii) landscape analysis should be incorporated in the process of modeling total N losses through denitrification.
Water‐Use Efficiency of Grasses as Affected by Soil, Nitrogen, and Temperature
Authors: Stout W. L. 
Published: July 2010

AbstractForage grass production in the northeastern USA is limited by soil water availability, but little is known about water use by forage grasses in this region. The purpose of this study was to assess the effects of soils, temperature regime, and N fertilization on water‐use efficiency of a C3 and a C4 forage grass. The study was conducted from 1987 to 1989 on four sites in central Pennsylvania selected for soil water‐holding capacity and temperature regime. Plot areas of orchardgrass (Dactylis glomerata L. cv. Pennlate) were treated with a split application of 0, 84, and 168 kg N ha−1 of 15N‐depleted NH4NO3. Plot areas of switchgrass (Panicum virgatum L. cv. Cave‐n‐Rock) were treated with a single application of 0 and 84 kg ha−1 unlabeled NH4NO3. Soil water was measured with a neutron probe on each plot biweekly during the growing season and monthly during the rest of the year. At heading stage (approximately 31 May), the orchardgrass plots were harvested for yield at a 7.5‐cm stubble height and all herbage removed from the plot. These plots were refertilized and sampled again on 31 October. Switchgrass was harvested at a 15‐cm stubble height at heading stage (approximately 15 July). Water‐use efficiency was 126 kg ha−1 cm−1 H2O for spring‐growth orchardgrass and 44 kg ha−1 cm−1 H2O for summer‐fall‐growth orchardgrass and was affected by N fertilization and temperature regime. Water‐use efficiency was 250 kg ha−1 cm−1 H2O for summer‐growth switchgrass and was also affected by N fertilization and temperature regime, but the effect of temperature was not as pronounced as in the case of orchardgrass.
Carbon Storage in Upland Forests of the Lake States
Authors: Grigal D. F. , Ohmann L. F. 
Published: July 2010

AbstractCarbon storage and dynamics are receiving increasing attention because of the hypothesized role of CO2 in global climate change. This study was carried out to determine total C storage in Lake States' forests, including C in biomass, forest floor, and mineral soil. Overstory trees were measured and samples of both forest floor and mineral soil (to 1 m) were collected from plots in 169 forest stands across Minnesota, Wisconsin, and Michigan. Five forest types were represented: balsam fir, Abies balsamea (L.) Mill.; jack pine, Pinus banksiana Lamb.; red pine, P. resinosa Ait.; aspen, Populus tremuloides Michx.; and northern hardwoods dominated by sugar maple, Acer saccharum Marsh. There were no strong geographic trends in C storage in biomass, forest floor, or mineral soil across the study area. Storage differed significantly among forest types. Each major C pool was related to a different set of descriptors. Total C storage, the sum of all pools, was related to forest type, stand age, available water, actual evapotranspiration, and soil clay content, explaining about 65% of the variation. Use of soil and site descriptors did not completely account for the strong effects of forest type on C storage. Differences in the size of C pools, as related to time since disturbance and forest type, indicate that C storage in forests of the Lake States can be influenced by forest management activities. Patterns of C storage in these moist temperate ecosystems are not as strongly influenced by climatic variables as is C storage in grasslands to the west.
Corn Growth as Affected by Suspension Fertilizers Containing Fluorosilicic Acid
Authors: Sikora F. J. , Copeland J P. , Dillard E. F. , Burnell J. R. 
Published: July 2010

AbstractFluorosilicic acid (H2SiF6) is a suggested additive to suspension fertilizers produced from monoammonium phosphate (MAP) to prevent gelling of the suspension. A greenhouse study was conducted to determine if F added to soil via P suspension fertilizers was detrimental to corn (Zea mays L.) growth. The F sources consisted of reagent‐grade NH4F, NH4SiF6, and three P suspension fertilizers. Equilibria constants and measurements with a F‐ ion selective electrode (ISE) indicated SiF62‐ dissociates to H4SiO4 and F‐ at pH > 4 and total F concentration <1 mM. Therefore, only F‐ needed to be considered as a potential toxic component in soils. At an initial soil pH of 5.8, an 11% dry‐matter weight decrease was observed when a suspension fertilizer with 89 g F kg−1 was added to soil to supply a rate of 170 mg F kg−1 soil. An adequate level of F in P suspension fertilizers is between 16 and 23 g kg−1 and this level did not affect corn dry‐matter weight with application rates ≤ 32 mg F kg−1 soil. At high soil F‐application rates from 30 to 170 mg F kg−1 soil, F was not suspected to be the phytotoxic agent since F concentrations in corn tops were all <0.4 mg kg−1. There was a significant correlation between soil Al and F extracted with water, which led to a hypothesis that decreased corn growth was due to Al phytotoxicity.
Soil pH Gradients near Calcite and Dolomite Particles
Authors: Stevens J. J. , Blanchar R. W. 
Published: July 2010

AbstractThe quality of liming material is normally judged by its neutralizing power, particle‐size distribution, and mineralogy. Historically, three methods have been used to evaluate these factors: (i) observing the effect of a liming material on crop yield, (ii) studying changes in soil pH with time after liming, and (iii) measuring unreacted carbonate. This study used a new method, glass pH microelectrodes, to evaluate the reactivity of limestone in soil. The effect of limestone particle size, mineralogy, and water leaching on the amount of unreacted carbonate and the soil pH around limestone particles was investigated. The reaction rate of calcite and dolomite was proportional to the surface area of the particles. Calcite reacted approximately twice as fast as dolomite. Reproduceable pH gradients exist around limestone particles in soil. In static systems, soil pH varied as a linear function of the reciprocal of distance from the particle surface. These gradients were generally independent of limestone particle size; however, in some cases pH was higher near larger particles. The soil pH next to dolomitic limestone particles was lower than near calcitic particles. Soil pH gradients around leached limestone particles were independent of the direction of water flow. The amount of limestone reacted in leached soil systems could be predicted from the number of particles and the shape of pH gradients around them in unleached soil systems.
Nutrient Distribution following Wheat‐Residue Dispersal by Combines
Authors: Douglas C. L. , Rasmussen P. E. , Allmaras R. R. 
Published: July 2010

AbstractUneven crop residue distribution by a combine may creae non‐uniform nutrient distribution in the field long after harvest. Uniform distribution of nutrients across a field has significant impacts on plant growth, soil sampling, fertilizer efficiency, and nutrient loss to surface and subsurface water. This study was conducted to evaluate nonuniformity of N, P, S, and K distribution across a field following combine harvest of soft white winter wheat (Triticum aestivum L.). Twelve self‐propelled combines were evaluated in 1983 and 10 in 1984. Each combine passed over an 11‐m strip of canvas, divided into 0.94 by 0.91 m segments, which was inserted in a swath cut into the unharvested wheat. Residues deposited on any segment of the canvas were collected and residue distribution and N, P, S, and K content of the residue was determined. Distribution of these four nutrients followed the residue distribution and created cyclic nonuniformity across the landscape. Maximum nonuniformity of nutrient distribution, where 1 = perfect uniformity, ranged from 2.7 to 9.0 for N, 1.9 to 7.7 for S, 2.3 to 9.4 for P, and 1.5 to 6.8 for K. Nutrient distribution was more extreme when wheat was cut closer to the ground. Combine modification to improve chaff distribution significantly improved nutrient distribution.