bluuebunny/crossref_metadata_2025_split huggingface dataset:
Texture, Climate, and Cultivation Effects on Soil Organic Matter Content in U.S. Grassland Soils
Authors: Burke I. C. , Yonker C. M. , Parton W. J. , Cole C. V. , Flach K. , Schimel D. S. 
Published: July 2010

AbstractSoil organic C content, a major source of system stability in agroecosystems, is controlled by many factors that have complex interactions. The purpose of this study was to evaluate the major controls over soil organic carbon content, and to predict regional patterns of carbon in range and cultivated soils. We obtained pedon and climate data for 500 rangeland and 300 cultivated soils in the U.S. Central Plains Grasslands, and statistically analyzed relationships between C and soil texture and climate. Regression models of the regional soils database indicated that organic C increased with precipitation and clay content, and decreased with temperature. Analysis of cultivated and rangeland soils indicated that C losses due to cultivation increased with precipitation, and that relative organic C losses are lowest in clay soils. Application of the regression models to a regional climate database showed potential soil organic matter losses to be highest in the northeastern section of the Central Plains Grasslands, decreasing generally from east to west. These statistical data analyses can be combined with more mechanistic models to evaluate controls of soil organic matter formation and turnover, and the implications for regional management.
Birdsfoot Trefoil Seedling Response to Soil Phosphorus and Potassium Availability Indexes
Authors: Russelle M. P. , Meyers L. L. , McGraw R. L. 
Published: July 2010

AbstractBirdsfoot trefoil (Lotus corniculatus L.) is a promising forage legume, yet little is known about its nutrient requirements during early growth. Several soil P and K indexes were evaluated for their ability to predict dry mass (DM) and P and K concentration and uptake by ‘Fergus’ and ‘Maitland’ birdsfoot trefoil seedlings grown for 6 wk in the greenhouse in four diverse soils amended to attain a broad range of plant‐available P and K. Soils were extracted with 0.01 M CaCl2, neutral 1 M ammonium acetate, or H2SO4 to estimate plant‐available K, and 1 mM SrCl2, Bray and Kurtz no. 1 (Bray‐P), or anion exchange resin (AER) to estimate available P. Shoot DM was not influenced by soil K and increased with increasing soil P, being best predicted across soils by AER‐P. Maitland DM exceeded that of Fergus at all fertility levels. Tissue concentration of P and K were best related to soil solution concentration (extracted with weak salt solutions), but only one‐half the variation in tissue P concentration was explained by soil solution‐P concentration. Across soils, P and K uptake were best related to Bray‐P and to solution‐K concentration, respectively, but exchangeable‐K exhibited less sensitivity to cultivar differences than solution‐K. Anion exchange resin appeared to extract a constant fraction of nonoccluded Fe‐ and Al‐bound P (47%), regardless of the oxide content of the soil, whereas the Bray‐1 reagent appeared to extract a constant proportion of P per unit mass Fe oxide present. These differences may account for the relatively poor performance of AER in predicting P uptake across soils differing in parent material.
Tillage and Surface Residue Effects on Evaporation from Soils
Authors: Steiner J. L. 
Published: July 2010

AbstractMany crop growth models require modification for dryland farming systems because they do not predict an effect of residues on the soil water balance. Daily evaporation (E) from a Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll) was measured in three experiments using laboratory cores or field microlysimeters to determine effects of tillage and residues on cumulative E and on E rate. The first experiment showed that the disk treatment had the highest rate of Stage 1 E and a lower slope of the Stage 2 E curve than sweep and no‐tillage treatments. Effects of tillage on surface wheat (Triticum aestivum L.) residues and on soil physical properties both seemed related to E. In a subsequent experiment, no effect of tillage‐induced differences in soil properties on daily E was measured when wheat residues were removed before tillage. In the third experiment the effect of cotton (Gossypium hirsutum L.), sorghum [Sorghum bicolor (L.) Moench], or wheat residue (x, m3 m−2) on the initial, energy‐limited rate of E (y, the potential E at the surface relative to bare soil E) was described by a logarithmic relationship [y = −0.99 − 0.236 (ln x), n = 36, r2 = 0.87]. With residues described on a mass/unit area basis, crop‐specific curves were obtained; but with residues described on a thickness or volume/unit area basis, the curves obtained with the different crop residues were very similar to the pooled relationship given above. This simple relationship between residue level and daily E can be incorporated into water balances of commonly used crop growth models to increase the accuracy of water balance prediction for different cropping systems.
Effect of Whole‐Tree Harvesting on the Sulfur Dynamics of a Forest Soil
Authors: Mitchell M. J. , Driscoll C. T. , Fuller R. D. , David M. B. , Likens G. E. 
Published: July 2010

AbstractSulfur constituents in the soil at the Hubbard Brook Experimental Forest are dominated by C‐bonded S and ester‐sulfate with smaller concentrations of adsorbed sulfate and ZnHCl‐reducible S forms. The relative proportions of these constituents are similar to those found in other Spodosols. Two years after a whole‐tree harvest of Watershed 5 there was a significant increase in adsorbed sulfate in the E and Bh horizons from 0.70 to 3.16 and from 2.73 to 4.96 kg ha−1, respectively, while organic S pools remained relatively constant except for some change in ester‐sulfate pools. This increase in sulfate in these horizons is consistent with patterns of soil solution and stream chemistry, which indicate increased sulfate adsorption due to acidification following mineralization of N, nitrification, and nitric acid leaching. Mass balance calculations comparing SO4 flux in stream water from watershed 5 with Watershed 6 (reference) accounted for 88% of the sulfate adsorbed in the E and Bh horizons of the former watershed. Organic S ranged 0.7 to 9.5 µmol S L−1 in stream and soil solutions. When this organic S is transported through the soil and deposited in the B horizon, it may serve as a large, stable pool of soil S, less subject to change than that of adsorbed sulfate.
Some Factors Limiting the Dissolution Rate of Phosphogypsum in an Acid Soil
Authors: Frenkel H. , Fey M. V. , Noble A. D. 
Published: July 2010

AbstractGranules up to 6 mm in diameter were collected in the field from an acid Natal soil (Palehumult) under cultivation, following reports of unexpected persistence of the material 2 yr after incorporation. The granules were subjected to a dissolution procedure employing electrical conductivity measurements of a stirred solution in which the granules were suspended in a perforated container. The rate of dissolution of the soiled granules which had first been washed in water to remove adhering soil was slower than that of the fresh granules pretreated in the same way. Scanning electron microscopy showed that a coating approximately 5‐µm thick enveloped the soiled granule. The coating was found by energy dispersive x‐ray analysis to contain a co‐concentration of Al and P. X‐ray diffractometric study of the water‐insoluble residue of scrapings from granule exteriors showed the presence of an unidentified, crystalline, lazulite‐like phase which could not be detected in the surrounding soil matrix or in the interior of the granules. The slow dissolution of the granules in the field soil is only partly due to the coating, however, with particle size being the dominant influence.
Wettable Porous Plastic for Use as a Porous Barrier in Soil Hydraulic Studies
Authors: McCoy Edward L. 
Published: July 2010

AbstractTwo grades of wettable porous plastic were examined for their applicability in water characteristic measurements and other soil hydraulic studies. The porous plastic is available in sheets (0.46 m wide, arbitrary lengths) and the two grades are composed of different amounts of polyvinyl chloride (PVC) and silica. Grade A‐20 exhibited a range of bubbling pressures between 62 and 69 kPa and a mean conductance of 0.20 h−1. Grade A‐40 exhibited a range of bubbling pressures between 21 and 35 kPa and a mean conductance of 1.60 h−1. These conductances generally exceed that of commonly employed porous barriers with comparable bubbling pressures. Comparison of the water retention curves of grades A‐20 and A‐40 indicate that grade A‐20 is more uniform, has lower porosity, and has smaller effective pore diameters with a narrower range of pore sizes. The porous plastic is easily cut to size by scissors and bonded to itself, PVC, or acrylic. The material is also durable and inexpensive.
Application of Fractal Mathematics to Soil Water Retention Estimation
Authors: Tyler Scott W. , Wheatcraft Stephen W. 
Published: July 2010

AbstractIn this paper, we present an analysis correlating the fitting parameter α in the Arya and Paris (1981) soil water retention model to physical properties of the soil. Fractal mathematics are used to show that α is equal to the fractal dimension of the pore trace and expresses a measure of the tortuosity of the pore trace. The fractal dimension of the particle‐size distribution can be easily measured and related to the α parameter of the Arya and Paris model. By suggesting a physical significance of the coefficient, the universality of the model is greatly improved. Soil water retention data, estimated strictly from particle‐size distributions, are proven to match measured data quite well. The fractal dimension of pore traces range from 1.011 to 1.485 for all but one soil tested.
Sand Detachment by Single Raindrops of Varying Kinetic Energy and Momentum
Authors: Sharma P. P. , Gupta S. C. 
Published: July 2010

AbstractSoil detachment by raindrops is a precursor to the start of interrill erosion and surface seal formation. Soil detachment occurs when erosive forces of raindrops are greater than the inherent strength of soil. Experiments were conducted to study the importance of inherent soil strength on detachment of soil by raindrops. Sand strength was controlled by varying matric potentials before raindrop impact. A range of raindrop kinetic energies and momentum was created by changing drop diameter (3.6–5.0 mm) and fall height (1–8 m). The experimental setup consisted of a varying height water drop former, an electronic drop discriminator, and a single‐drop soil splash collector. Splash collected by varying drop height of a 4.6‐mm‐diam. drop on sand equilibrated at a matric potential (ψm) of −1.5 kPa (higher strength) showed that a larger threshold energy is needed to initiate soil detachment than when equilibrated at ψm = −0.1 kPa (lower strength). Also, the threshold erosivity was larger in magnitude and more significant when using momentum as an index of erosivity instead of kinetic energy. The relationships between sand splash and erosivity were linear (P < 0.001) for raindrops with diameters of 3.6 to 5 mm falling from heights of 0.76 to 7.6 m on sand equilibrated at ψm = −1.0 kPa. Sand splash was represented by a model of the form D = Kd[E − Eo]b, where D is detachment, E is raindrop erosivity, Eo is threshold erosivity, Kd is sand detachability, and b is an exponent equal to 1. This equation of describing soil detachment as a function of erosivity is an improvement over the currently used nonlinear relationship of the form D = Kd Eb.
Relationship Between Soil Potassium Forms and Mineralogy
Authors: Sharpley Andrew N. 
Published: July 2010

AbstractThe relationship between soil K forms (water soluble, exchangeable, HNO3‐extractable, and mineral) as a function of clay mineralogy and taxonomy, was determined using 102 soils from the continental USA and Puerto Rico, representing 10 soil orders. These relationships may have use in evaluating potential soil K fertility and prediction of K cycling and plant uptake. The soils were divided into three groups (kaolinitic, mixed, and smectitic) based on dominant mineralogy of the clay fraction. For each group of soils, water soluble K was related to exchangeable K content (r2 of 0.86 to 0.96), with exchangeable K solubility increasing from smectitic, mixed, to kaolinitic soils. For each group, exchangeable K was also related to HNO3‐extractable K (r2 of 0.81 to 0.83), thus, the capacity to supply K under continuous cropping, is greater for smectitic than kaolinitic soils of similar exchangeable K contents. Mineral K was a function of clay content for each soil group (r2 of 0.66 to 0.90). Using these relationships, water soluble (2–37 mg kg−1), HNO3‐extractable (21–2691 mg kg−1), and mineral K contents (1.59–16.93 mg kg−1) of 60 independent soils, were closely predicted (r2 of 0.78 to 0.96) from exchangeable K, clay content, and clay mineralogy. These results indicate that determination of both exchangeable and HNO3‐extractable K could give a better indication of the potential K supplying power of a soil. Further, the relationships obtained will allow determination of initial soil K pool sizes from readily available soil taxonomic, clay mineralogy, and chemical properties, for use in modeling the cycling and plant uptake of soil K.
Ammonium Fixation by High‐Charge Smectite in Selected Texas Gulf Coast Soils
Authors: Chen Cy‐Chain , Turner Fred T. , Dixon Joe B. 
Published: July 2010

AbstractThe Beaumont (fine, montmorillonitic, thermic Entic Pelludert) and Lake Charles (fine, montmorillonitic, thermic Typic Pelludert) soils along the Texas Gulf Coast produce only about 2 Mg rice (Oryza sativa L.) ha−1 without N fertilizer, while the Nada soil (fine, montmorillonitic, thermic Typic Albaqualf) frequently produces 5 Mg ha−1. In studying differences between these soils, data showed that NaCl applied to the Beaumont soil did not reduce rice yield, but equivalent amounts of KCl did. The KCl‐induced yield reduction may have been the result of NH+4 entrapment in clay minerals caused by added K. Clay mineral characterization showed that the Beaumont soil fixed more NH+4 than the Nada soil because the Beaumont soil was higher in soil K, high‐charge smectite [i.e., 0.76 equivalents per (Si,Al)4O10(OH)2] and charges in the tetrahedral sites. The 8‐wk incubation of Beaumont soil in the rice root zone resulted in partial release of added Nh+4 and no release of native NH+4 when the Beaumont soil had been Ca saturated. The K‐saturated Beaumont soil did not release fixed Nh+4 during incubation as the Ca‐saturated soil did. The Lake Charles soil showed clay and fixation characteristics similar to the Beaumont soil, while the Nada soil did not fix beyond its native level or release any upon incubation. The presence of 2:1 layer silicates in Beaumont and Lake Charles soils with x‐ray diffraction characteristics similar to smectite, and NH+4 fixation characteristics similar to vermiculite, was recognized.
Comparison of the Titration and Ion Adsorption Methods for Surface Charge Measurement in Oxisols
Authors: Marcano‐Martinez E. , McBride M. B. 
Published: July 2010

AbstractThe pH‐dependent charge properties of the A and B horizons of two representative oxisols from the Cerrado Region, Brazil, were studied by a comparison of the potentiometric titration method of net charge measurement and direct measurement of anion and cation exchange capacity from K+ and Cl‐ adsorption. Most soil samples bore net negative charge at their native pH, but variability in the magnitude of this charge was attributed to the effect of Al‐blocked exchange sites or contributions from strongly acidic organic functional groups, since these soils had similar mineralogies. The soils also bore significant pH‐dependent positive charge at their natural acidic pH values, which was more evident in the B horizons than the surface horizons. Estimates of net surface charge by potentiometric titration and ion adsorption did not agree, especially as the soil pH was adjusted away from the point of zero charge. This lack of agreement is attributed to dissolution reactions of minerals and organic matter at high and low pH, which consume acid or base and overestimate surface charge.
Phosphorus‐31 Magic Angle Spinning Nuclear Magnetic Resonance of Wastewater Sludges and Sludge‐Amended Soil
Authors: Hinedi Zeina R. , Chang Andrew C. , Yesinowski James P. 
Published: July 2010

AbstractPhosphorus‐31 magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy was used to examine the forms of P in two municipal sludges and a sludge‐amended soil. The signal‐to‐noise ratio and the resolution of the spectra improved considerably when paramagnetics in the sludge and sludge‐treated soil samples were removed by a reducing treatment involving citrate‐bicarbonate‐dithionite (CBD). The spectra suggested that the P solid phases in the anaerobically digested sludge from Los Angeles County, California were calcium phosphates. The strong paramagnetic effects, however, precluded more precise identification of the calcium phosphate phase. In the anaerobically digested alum‐treated sludge from Riverside, three P solid phases are detected, carbonated apatite, a pyrophosphate, and aluminium phosphate. In the Domino soil (fine‐loamy, mixed, thermic Xerollic Calciorthid), amended with sludge from Los Angeles County, 31P MAS NMR indicated the presence of carbonated apatite and pyrophosphate solid phases.
Pedogenic Factors Affecting Magnetic Susceptibility of Northern California Soils
Authors: Singer Michael J. , Fine Pinchas 
Published: July 2010

AbstractMass magnetic susceptibility (χ) was measured on samples taken from horizons from 27 northern California soils to determine the amount and vertical distribution of χ, and if the observed χ distribution could be related to parent material, climate, topography and time. In most of the soils with vertical morphological distinctions, eluvial horizon χ was greater than illuvial, R or CR χ. This susceptibility enhancement was interpreted as being due to pedogenic processes. Soils formed on parent material rich in Fe‐bearing minerals (e.g. basalt) had higher absolute χ and greater χ enhancement than did soils formed on Fe‐poor parent material (e.g. siltstone). Enhancement was greater in soils from areas of high (>1000 mm) mean annual precipitation compared with areas of low (<500 mm) mean annual precipitation, and soils formed under mean annual temperature ≤6 °C had less distinct enhancement than soils formed in warmer temperature regimes provided the precipitation was the same. Two soils with poor and somewhat‐poor drainage classes had distinctly lower absolute χ than associated well‐drained soils. Both absolute χ in eluvial horizons and susceptibility enhancement of eluvial over illuvial, and eluvial over C horizons increased as soils became older. Older soils were enhanced to a greater depth than younger soils. Eluvial and illuvial χ was greater than parent material χ in most profiles because non‐ or weakly magnetic minerals were converted to maghemite, which accumulated in eluvial horizons. In young soils with little morphological differentiation formed on transported parent material, χ measurements help to locate lithologic discontinuities.
Relationship of Soil Crust Morphology to Inter‐rill Erosion Parameters
Authors: Remley P. A. , Bradford J. M. 
Published: July 2010

AbstractResearch on soil surface sealing and crust formation has taken two approaches: (i) measurement of common soil erosion parameters such as infiltration, permeability, detachment, and strength and (ii) observation of seal or crust morphology using both microscopic and submicroscopic techniques. The purpose of this research was to combine the two approaches to extend our knowledge of surface sealing and crusting and its role in the erosion process. Eight soils with exchangeable sodium percentages (ESP) <1 and with textures ranging from sandy loam to clay were exposed in the laboratory to simulated rainfall with an intensity of 63 mm h−1 for 1 h. Seal and crust formation were investigated by measuring splash and wash erosion, single waterdrop splash, and fall‐cone strength and by observing scanning electron microscope (SEM) and thin‐section photographs. Medium‐textured soils (five silt loams and a silty clay loam) developed homogeneous, silty surface seals of high strength ranging from 14 to 43 kPa and low splash detachment. Splash amounts for single drop impact ranged from 0.8 to 1.8 mg soil per drop, and for multiple raindrops in erosion pans, from 9 to 26 g soil during the final 5 min of a 60 min rain. For a clay soil, no morphological evidence of crusting was observed; strength of the seal was low (6.4 kPa) and splash amount was high (40.0 g in 5 min). For a sandy loam soil, splash was high (41.8 g) and strength, low (10.8 kPa). Crust morphology indicated slight crusting. The subjective nature of interpreting SEM and thin section photographs makes it difficult to draw conclusions about erosion processes or rates.
Nitrogen Isotope Fractionation in Burned and Unburned Chaparral Soils
Authors: Herman D. J. , Rundel P. W. 
Published: July 2010

AbstractPlant and soil processes involving N‐transformations have been monitored by techniques measuring the 15N/14N ratio in a sample relative to the atmosphere (δ15N). Unusually low δ15N values have been reported in the tissues of chaparral shrubs. The primary objective of this study was to investigate soil N‐cycling processes which may yield the low plant tissue δ15N levels. Since the chaparral is subject to periodic brush fires, which in turn result in high levels of inorganic N‐forms in the soil during the first year following the burn, possible effects of burning on soil δ15N were also investigated. Incubations were conducted on soils from an area which had been subjected to a brush fire, and an adjacent unburned area; both soils are fine, thermic, schistose, very steep Ultic Haploxeralfs. Concentrations and δ15N of soil NH+4 and NO‐3 were periodically measured. A C‐ and N‐rich ash resulted in rapid mineralization of N in the burned soil; a substrate more resistant to biological degradation resulted in an initial loss, then subsequent slow accumulation of inorganic‐N in the unburned soil. Nitrate was the dominant mineral species in each soil after a few weeks. As nitrification progressed, δ15N of NH+4 increased and δ15N of NO‐3 decreased. Since the mineral pool in each soil became dominated by NO‐3, δ15N of the mineral pool became strongly negative. A mathematical model of isotope dynamics fits empirical data well.
Simulation of Soil Water Above a Water Table in a Forested Spodosol
Authors: Phillips L. P. , Comerford N. B. , Mansell R. S. , Neary D. G. 
Published: July 2010

AbstractThe relationships between soil water potential and water table depth in the upper five horizons of an Ultic Haplaquod of the lower Coastal Plain flatwoods are described. Soil water pressure head in the E, Bh, Bs, and E′ horizons was in hydrostatic equilibrium with the underlying water table during all conditions when water was perched above an argillic horizon. The A horizon was in equilibrium with the water tables only when water tables were <65 to 70 cm from the soil surface. Water pressure heads and contents in the soil profile were simulated using a finite‐difference, one‐dimensional, unsaturated water‐flow model. Simulations of water pressure head were excellent for the lower horizons (E through E′) under all conditions, and poor for the A horizon. During high water tables, water pressure head simulations for the A horizon were improved. Fewer discrepancies between measured and simulated conditions occur when water pressure head values are converted to volumetric water contents. Unfortunately, the water‐flow model described here did not adequately handle high infiltration rate rainfall events experienced at the site. It is concluded that in these sandy soils: (i) water content is the preferred prediction variable; and (ii) further advances in mechanistically modeling water uptake from each soil horizon in forest ecosystems will be limited by adequate information on plant root biology.