bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hardsetting Soils in Southeast Australia: Landscape and Profile Processes
Authors: Franzmeier D. P. , Chartres C. J. , Wood J. T. 
Published: July 2010

AbstractHardsetting soil horizons are relatively soft when moist but become unusually hard when dry. Soils with these horizons are common in Australia and elsewhere. They have been studied mainly in exposures such as road cuts where their development is most marked. The main objective of this study was to elucidate the relationships between landscape position and hardsetting processes. Soils were sampled along two transects that start in bedrock hills, cross broad eolian‐fluvial plains, and terminate in a local flood plain or lacustrine basin. They are mainly Dystrochrepts, Palexeralfs, and Natrixeralfs, and many soils are aquic intergrades. Samples were analyzed using standard characterization methods, and extracted with water, oxalate solution, and citrate‐bicarbonate‐dithionite solution; Fe, Al, and Si contents were determined from the extracts. Soil strength was characterized by the modulus of rupture test. Strength was partly related to clay content, but several E and BE horizons were very strong relative to their clay content, thus hardsetting. They were in the zone of the pedon in which exchangeable Na and pH increased sharply with depth. This sodicity was also cyclic in the landscape. Strength was correlated positively with extractable Si and negatively with extractable Al. In hardsetting soils, which tend to have impeded drainage, Fe‐oxide minerals periodically precipitate and dissolve. We postulate that silica is dissolved and dispersed in upper horizons with a large pH gradient, moves down the profile, and bonds with Fe‐oxide minerals on clay surfaces. The bonds strengthen on drying to form hardsetting horizons.
Vegetation Management and Interrill Erosion in No‐Till Corn Following Alfalfa
Authors: Gallagher A. V. , Wollenhaupt N. C. , Bosworth A. H. 
Published: July 2010

AbstractNo‐till corn (Zea mays L.) following alfalfa (Medicago sativa L.) is recommended for reducing soil erosion; however, killing alfalfa in the fall may result in insufficient crop residue cover for Conservation Compliance soil erosion goals. We hypothesized that soil conservation effectiveness was related to burn‐down spray date and final harvest date influence on cover. A Wisconsin field study to test this hypothesis included fall and spring burn‐down spray dates in combination with either August or September final alfalfa harvests. Soils included Plano and Saybrook silt loams (fine‐silty, mixed, mesic Typic Argiudolls) on 2 to 9% slopes and Palsgrove silt loam (fine‐silty, mixed, mesic Typic Hapludalf) and Reedsburg silt loam (fine‐silty, mixed, mesic Aquic Paleudalf) on 7 to 14% slopes. Simulated rainfall (72 mm h−1 for 1 h) was applied following corn planting. The fall spray‐September harvest (FS‐SH) averaged 25% residue cover, measured after planting, with soil loss of 257 g m−2. The spring spray‐August harvest (SS‐AH) averaged 79% residue cover and 24 g m−2 soil loss. Of the 72 mm of rain applied on each of the treatments, 34 mm ran off the two FS treatments, 23 mm ran off the SS‐SH treatments, and 19 mm ran off the SS‐AH treatments. Treatment runoff amounts and final infiltration rates related in part to surface macroporosity and surface sealing. Fall herbicide application resulted in too little residue cover to adequately reduce soil erosion.
The Fate of Sludge Phosphorus in Soil‐Plant Systems
Authors: Frossard E. , Sinaj S. , Zhang L‐M , Morel J. L. 
Published: July 2010

AbstractSewage sludges have been used for many years as sources of P for agricultural crops, but there is a lack of information regarding the proportion of sludge P that can be used by crops. The aim of this work was to assess the importance of soil available P and sludge origin on the utilization of sludge P by plants. First, the changes in soil P isotopically exchangeable within 1 min (E1min) were measured in incubated soil‐sludge mixtures using two soils and four sludges. Then, the uptake of sludge P by ryegrass (Lolium perenne L.) was measured on the same sludge‐amended soils. The application of sludges increased E1min to values lower or equal to those obtained following the application monocalcium phosphate. Similarly the utilization of sludge P by ryegrass was systematically lower than the utilization of P derived from a water‐soluble fertilizer. In both soils, the lowest utilization of sludge P was observed for the two FeSO4 flocculated and anaerobically digested sludges, while the primary sludge and the aerobically digested sludge released somewhat higher quantities of P to ryegrass. In the clayey soil, the amount of sludge P taken up by the crop was significantly related both to the sludge and soil available P content, whereas no such relation was observed in the loamy soil because of its high available P content. The origin of the sludge and the soil available P content must therefore be taken into account when advising sludge application to crops to adjust P inputs to plant needs.
A Modified Number‐based Method for Estimating Fragmentation Fractal Dimensions of Soils
Authors: Kozak E. , Sokołowska Z. , Stępniewski W. , Pachepsky Ya. A. , Sokołowski S. 
Published: July 2010

AbstractFractal theory has been applied to the characterization of particle‐ and aggregate‐size distributions in soils. We used a number‐based method for estimating fragmentation fractal dimensions from these distributions. This method has several inconsistencies. The objectives of our study were to: (i) propose a modified number‐based method, (ii) evaluate the modified method using published data on particle‐ and aggregate‐size distributions, and (iii) apply the modified method to a large particle‐size distribution data base to analyze the validity of fractal scaling. Assuming scale‐invariant fragmentation to be a valid model of particle‐size distribution within size ranges of fractions, we derived a formula expressing the characteristic grain size as a function of the fractal dimension and limits of the grain size range. Parameters of Turcotte's fractal fragmentation model were found by minimizing the sum of squares of differences between measured and calculated masses of grain fractions. Comparison between original and modified number‐based methods showed that the modified method generally resulted in lower fragmentation fractal dimensions than the original method. The modified method was applied to a data set of particle‐size distributions of 2600 soil samples. In 80% of samples, the fractal scaling was not applicable across the whole range of particle size between 0.002 and 1 mm, since errors of the fractal fragmentation model were statistically significantly larger than measurement errors, and estimates of the fractal dimension were larger than 3. It appears that models more sophisticated than scale‐invariant fragmentation are required to simulate soil particle‐size distributions.
Solute Transport under Transient Flow Conditions Estimated Using Time Domain Reflectometry
Authors: Risler P. D. , Wraith J. M. , Gaber H. M. 
Published: July 2010

AbstractImproved methods having high resolution in space and time are needed to monitor transport of soluble chemicals in soils. We used time domain reflectometry (TDR) to measure breakthrough curves (BTCs) for Br− during miscible displacement in repacked soil columns under nonsteady water flow conditions. A simple linear model was used to estimate soil solution electrical conductivity (σw) based on TDR‐measured bulk soil electrical conductivity (σa) and volumetric water content (θ). An efficient calibration method was developed whereby required model parameters were estimated in the same soil volume and under the same flow conditions as were used in subsequent transport experiments. Breakthrough curves measured using TDR were similar to those based on electrical conductivity or Br− concentration in effluent fractions, although peak σw were substantially lower for TDR than for effluent from two of the four soils. Effluent σw BTCs were adequately predicted based on TDR σa and θ for all four soils when parameters of the simple linear model or two alternative models were optimized to the effluent data. Time moments and convection‐dispersion equation (CDE) transport parameters based on time moments of measured BTCs were similar for TDR and effluent analyses. Our results indicate that TDR has potential to monitor the status of representative concentrations of ionic solutes under laboratory and field conditions, without the need to impose steady water flow.
Determination of Arsenic Species in Soil Solution under Flooded Conditions
Authors: Onken B. M. , Hossner L. R. 
Published: July 2010

AbstractGreenhouse experiments were conducted to evaluate the relationships between the species and concentrations of As in the soil solution of flooded soils with other parameters including soil pe, pH, Fe, Mn, and type and amount of As added. Two soils were treated with 0, 5, 15, 25, 35, and 45 mg As kg−1 soil added as either Na‐arsenate or Na‐arsenite and planted with rice (Oryza sativa L.). Soil solution samples were collected during a period of 60 d and analyzed for As. Selective hydride generation was employed to evaluate both type and quantity of As present in the samples. Inorganic As in the form of arsenate and arsenite was found in the soil solution of both soils. The conversion of added arsenite to arsenate occurred within the first 10 d of the experiment when the pe/pH of the soil was not conducive to arsenite stability. Added arsenate was converted to arsenite during the course of the experiment as the pe/pH of the soil declined due to flooding. Arsenate reached a maximum in soil solution at 10 to 20 d after flooding while maximum arsenite concentrations occurred at 20 to 30 d after flooding. The total concentration of As in soil solution generally reached a maximum at 20 to 30 d after flooding, after which time precipitous losses of As from soil solution occurred in all but the highest As treatments. Soil solution As concentrations were not statistically different between planted and unplanted controls.
Aspartase Activity of Soils
Authors: Senwo Z. N. , Tabatabai M. A. 
Published: July 2010

AbstractThe enzyme aspartase [L‐aspartate ammonia‐lyase, Enzyme Commission (EC) 4.3.1.1] catalyzes the hydrolysis of L‐aspartate producing fumarate and NH3. The detection of this enzyme in soils is reported, and a simple and precise method is described for assaying its activity in soils. The method involves determination, by steam distillation, of the NH4+‐N produced when soil is incubated with potassium aspartate in 0.1 M THAM [tris(hydroxymethyl)aminomethane] buffer (pH 8.5) and toluene at 37°C for 24 h. Results showed that soil aspartase has its optimum activity at buffer pH 8.5 and is inactivated at temperatures above 40°C. Preheating soil samples for 2 h before assay of aspartase activity showed that the enzyme is stable up to 40°C in field‐moist samples and up to 70°C in air‐dried samples. The Km values of the aspartase activity in three soils ranged from 0.173 to 0.208 M. The Arrhenius equation plot for aspartase activity in three soils was linear between 20 and 40°C. The activation energy values of the reaction catalyzed by this enzyme ranged from 40.1 to 50.7 kJ mol−1, and the temperature coefficients (Q10) ranged from 1.50 to 2.44 (avg. = 1.89). Treatment of soils with formaldehyde, dimethylsulfoxide, and HgCl2 decreased the aspartase activity but toluene increased this activity. The use of sulfhydryl reagents suggested that a free sulfhydryl moiety is present in the active sites of this enzyme. The coefficients of variation of the proposed method for assay of aspartase activity in soils was <2.5%.
Tillage and Nitrogen Placement Effects on Nutrient Uptake by Potato
Authors: Westermann D. T. , Sojka R. E. 
Published: July 2010

AbstractDeep tillage of compacted soils can improve potato (Solanum tuberosum L.) tuber yield and quality if no other production factors are limiting. We hypothesized that within‐row subsoiling and N placement would affect tuber yields and availability of plant nutrients. Potato (cv. Russet Burbank) was grown after winter wheat (Triticum aestivum L.) in 1989 and after dry bean (Phaseolus vulgaris L.) in 1990 on a furrow irrigated Portneuf silt loam (coarse‐silty, mixed, mesic Durixerollic Calciorthid). Fall tillage treatments (disking, chiseling, and moldboard plowing) were split with zone subsoiling after planting. Nitrogen was broadcast before planting or banded beside the seed piece at planting across all tillage combinations. We estimated plant nutrient status and uptake each year with whole‐plant and petiole samplings during tuber growth. Final tuber yield and quality were determined in early October. Fall tillage did not influence nutrient concentration and uptake, tuber yield, or quality. Zone subsoiling increased average plant dry weights 9%, total tuber yields 10% (4 Mg ha−1), and quality, and increased P uptake an average of 11.6% (1.8 kg P ha−1) without appreciably changing whole‐plant or petiole P concentrations. Banding N increased average plant dry weight 6.4%, total tuber yield 9%, and N uptake 28% compared with broadcast N. Petiole NO3‐N, P, K, and Zn concentrations were higher where N was banded. There were no consistent zone subsoiling × N placement interactions. Higher nutrient applications may be required with zone subsoiling or to compensate for soil compaction problems.
Spatial Variability Patterns of Phosphorus and Potassium in No‐Tilled Soils for Two Sampling Scales
Authors: Mallarino Antonio P. 
Published: July 2010

AbstractThe increasing use of grid soil sampling methods and variable‐rate fertilization requires better understanding of patterns and causes of lateral variability of nutrients. This study assessed patterns of spatial variability of P and K for two scales of sampling on eight no‐tilled corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] fields. The fields had received no P or K fertilization since the last harvest but had varied histories of fertilization. Fifty 10‐core (0‐ to 15.2‐cm depth) composite samples were collected from 2.2‐m2 areas separated 3.05 m from each other along each of two 150‐m intersecting transects laid out across and along old crop rows. Sixty‐seven single‐core samples spaced 7.6 or 15.2 cm were collected from 7.85‐m segments of the transects across rows. Variography revealed high random and spatially structured variability for most fields. The structure of the variability differed among fields and directions within a field. Plots of soil‐test P and soil‐test K values, fast Fourier transform analyses, and semivariograms showed clusters and periodic patterns of variable regularity and size across fields. The cyclic patterns were more defined across crop rows. Small‐scale cyclic patterns with a period of ≈ 1 m revealed for some fields probably resulted from repeated banded fertilizer applications. Large‐scale cyclic trends with periods of 15 to 18 m or a multiple of this distance were probably the result of broadcast fertilization with commercial bulk spreaders. Sampling methods should be developed for fields with high spatial variability of cyclic structure at various scales. Producers should pay more attention to uniform application of fertilizers and manure.
Water‐Holding Characteristics of Metasedimentary Rock in Selected Forest Ecosystems in Southwestern Oregon
Authors: Zwieniecki Maciej A. , Newton Michael 
Published: July 2010

AbstractOn sites characterized by shallow soil in semiarid climates, lack of bedrock description may lead to underestimates of total storage capacity of water available for plants, and therefore of potential site productivity. Sample rocks from southwestern Oregon soil‐rock profiles excavated beneath typical forest plant communities were examined for pore volume distribution by means of mercury intrusion porosimetry and oversolution equilibrium. Four ranges of pore size were distinguished: gravitational water, available water content (AWC), slowly available water (SAW), and nonavailable water. Pore volume for AWC and SAW was associated with bulk density and in low density rock, was 20% of volume. Results suggest that metasedimentary rock has the potential to be a major reservoir of plant available water in semiarid climates.
Limitations of Bioassays for Monitoring Forest Soil Productivity: Rationale and Example
Authors: Burger James A. 
Published: July 2010

AbstractSustaining forest soil productivity is a common goal of forest landowners in the Southeast, but determining the effects of forest management practices on soil and site quality has not been easy. An unbiased measurement is needed to monitor sustained soil and site productivity. Growth cycle comparisons, traditional measures of forest productivity, are not very timely, are often biased, and do not always account for changes in soil quality due to management. This was demonstrated by comparing growth curves of two successive loblolly pine (Pinus taeda L.) rotations, and by comparing growth curves influenced by two site preparation treatments within the last rotation. The growth cycle comparison between rotations was not a definitive indicator of sustained soil quality because stand response could have been confounded by differences in genotype and vegetation management from the first to the second rotation. Stand responses due to soil treatment in the last rotation were confounded by the influence of different levels of competing vegetation. Because stand response is a function of many confounding non‐soil factors as well as soil quality, soil sustainability and the effects of management should be determined by measuring soil properties and processes directly.
Field Evaluation of Passive Capillary Samplers
Authors: Brandi‐Dohrn Florian M. , Hess Mario , Selker John S. , Dick Richard P. 
Published: July 2010

AbstractSoil solution samplers have certain inadequacies that limit their range of possible applications. Passive capillary samplers (PCAPS), which apply suction to the soil pore water via a hanging water column in a fiberglass wick, have shown promising results in preliminary experiments in regard to collection efficiency of water and Br tracers. The objectives of this study were to evaluate PCAPS with respect to (i) effect of installation procedure and operational characteristics; and (ii) ability to estimate the soil‐water and solute flux. We installed 32 PCAPS and 32 ceramic suction cup samplers at a depth of 1.2 m in an undisturbed silt loam soil. For the first year, water flux, NO3‐N and Br concentrations in the part of the PCAPS closest (0.3 m) to the refilled trench were 15, 14, and 34% less, respectively, than in the part farthest (0.9 m) away from the refilled trench. This was attributed to installation procedure, since the bias ceased for the second year. Soil‐water flux measurements of PCAPS underestimated those determined by a water balance by 20 to 34%. Some of the discrepancy is thought to be due to the lack of accounting for runoff, which was observed but not quantified. The recovery of a Br tracer was low with an average of 29%, ranging from 5 to 77%, which was attributed to lateral water movement due to prominent lateral stratification. To estimate the mean Br concentration with a 30% bound at the 0.05 confidence level on this 1‐ha field site, 25 PCAPS and 37 suction cup samplers are necessary. Sampling a more evenly distributed solute such as residual fertilizer NO3 requires only eight PCAPS for this level of confidence.
BTEX Sorption by Organo‐Clays: Cosorptive Enhancement and Equivalence of Interlayer Complexes
Authors: Jaynes W. F. , Vance G. F. 
Published: July 2010

AbstractAqueous organic contaminants, such as gasoline‐derived aromatics, are effectively sorbed by organo‐clays. Organo‐clays were prepared from montmorillonite (SWy‐1, SAz‐1) and vermiculite (VSC) clay minerals by exchanging quaternary, alkylammonium cations for the inorganic exchange cations; thus, a variety of clay‐charge/organic‐cation combinations were formed. Dodecyltrimethylammonium (DTMA), hexadecyltrimethylammonium (HDTMA), didodecyldimethylammonium (DDDMA), and dioctadecyldimethylammonium (DODMA) organic cations were used. An aqueous mixture of BTEX (benzene, toluene, ethylbenzene, xylenes) consistent with unleaded gasoline was used to relate organo‐clay sorptivity to structure. Greater sorption of the BTEX mixture constituents than the pure compounds occurred when total sorbed BTEX loadings on the organo‐clays exceeded 10 g/kg. A cosorption effect caused curvilinear isotherms and enhanced BTEX mixture sorption; BTEX sorption increased the organo‐clay organic matter content, which promoted additional BTEX sorption. The sorptivities of the organo‐clays were generally proportional to the organic C contents; although SAz‐DDDMA and VSC‐HDTMA, with 20 to 30% less C, had twice the BTEX sorptivity of SAz‐DODMA and VSC‐DDDMA. No relationship was found between surface area and BTEX sorption. A straight‐chain alkyl cation conferred five times greater BTEX sorption to an organo‐clay than did a comparable cyclic alkyl cation. This suggests that rearrangements in the alkyl groups may facilitate sorption in a manner analogous to solvation. Organo‐clay BTEX sorptivity was governed by the type of alkylammonium complex; a paraffin complex with a 25.4 to 27.6 Å basal spacing was optimal. Organo‐clays of similar basal spacing prepared using different clays and alkylammonium cations had equivalent sorptive phases. Selection of an appropriate combination of clay and organic cation can optimize contaminant sorption by organoclays.
Fractal Dimension of Humic Acids in Aqueous Suspension as a Function of pH and Time
Authors: Senesi N. , Rizzi F. R. , Dellino P. , Acquafredda P. 
Published: July 2010

AbstractThe fractal dimensions of soil and peat humic acids equilibrated for various lengths of time in aqueous suspension at different pH values were determined by measuring their turbidity as a function of wavelength, with collaboration by scanning electron microscopy (SEM). Particle‐size distributions of the humic acid systems were also determined. The analysis of the power‐law dependence of the turbidity on the wavelength revealed that soil and peat humic acids may exhibit either a nonfractal or a mass fractal nature. Peat humic acid could also be described as a surface fractal. The passage from one regime to another depended on the pH and equilibration time. With an increase of either factor, the mass fractal dimension of humic acids decreased from about 2.8 to values close to 1.0. This trend, supported by SEM observations, suggested that humic particles in suspension evolve from compact, almost space‐filled structures with smooth surfaces, to less compact, fragmented and elongated structures with increasingly rough and irregular surfaces as the pH or time increases. Values of the mass fractal dimension close to 2.5 would reflect diffusion‐limited aggregation (DLA), whereas values close to 2.1 would suggest a reaction‐limited cluster‐cluster (RLA) aggregation model for humic acid. The fractal dimension thus represents a numerical parameter able to describe quantitatively the morphological features assumed by humic particles in suspension and to provide information on the underlying aggregation processes.