bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temporal and Spatial Soil Variability on Three Forested Landtypes on the Mid‐Cumberland Plateau
Authors: Hammer R. David , O'Brien Ralph G. , Lewis Russell J. 
Published: July 2010

AbstractTemporal and spatial variability of selected soil chemical properties were determined within and among three forested mid‐Cumberland Plateau landtypes at two locations. Major soils included Typic Fraguidults on uplands, Humic Hapludults on slopes, and Aquic Dystrochrepts in first‐order bottoms. Temporal soil variability was measured at monthly intervals for 25 consecutive months from samples taken from 0.5‐ by 0.5‐m subplots within two 2.5‐ by 2.5‐m plots on each landtype. Spatial variability samples were collected from similar, adjacent plots during a 1‐week period. A total of 300 spatial and 300 temporal observations were taken for each soil property in each of three soil horizons. Extractable Ca, Mg, and K, and pH in H2O and KCl were measured for A, AB, and Bt horizons, and total C was determined for A horizons. Magnitudes of variability were statistically compared using a procedure robust for nonnormally distributed data. Magnitudes of soil variability were significantly related to landtypes at the Bonferroni significance level. Only three of 16 soil variables differed in magnitudes of spatial vs. temporal variability. Variability on sites was of the order slopes > bottoms > uplands. Soil morphological features and parent materials appeared to strongly influence magnitudes of temporal and spatial variability.
Floodwater Properties, Nitrogen Utilization, and Nitrogen‐15 Balance in a Calcareous Lowland Rice Soil
Authors: De Datta S. K. , Fillery I. R. P. , Obcemea W. N. , Evangelista R. C. 
Published: July 2010

AbstractLarge areas of lowland rice (Oryza sativa L.) soils in South and Southeast Asia are calcareous. Field studies in the 1983 dry and wet seasons evaluated the effects of N source and application method on N loss and N utilization in a calcareous clay loam soil using the 15N‐balance technique. In the 1983 wet season and the 1984 dry season, crop recovery of the residual 15N remaining after the first crop was determined. When urea supergranules (USG) were deep point‐placed, the partial pressure of ammonia (pNH3) in the floodwater was negligible. High floodwater pNH3 was calculated with split application of fertilizer. Farmers' split of prilled urea (PU) gave the highest pNH3 (0.44 Pa in the wet season). pNH3 in the floodwater peaked on the third day and dropped to negligible thereafter. Deep placement (10 cm) of USG had the highest grain yield in the dry season. Ammonium sulfate produced a yield similar to that of urea. The highest 15N recovery by the crop (straw + grain) was 78% in the dry season and 64% in the wet season with deep point placement of USG. Nitrogen‐15‐balance data showed that with point placement of USG, 3% N was not accounted for after harvest in the dry season and 10% in the wet season. In contrast, when urea or ammonium sulfate was split‐applied using improved timing and water management (researchers' split), 26 to 28% of applied N was not recovered at harvest in the dry season and 36 to 41% in the wet season. Soil N fractionation showed that 14 to 26% of 15N‐labeled fertilizer was immobilized into the acid‐hydrolyzable organic N fraction in the dry season and 9 to 18% in the wet season. With point placement of USG and band placement of urea, the decrease in the value of hydrolyzable organic N fraction at harvest indicated N release for plant use during the cropping season. Applied N immobilized into the nonhydrolyzable organic N and fixed in the nonexchangeable N was not significant.
Fine Clay Mineralogy of Soil Matrices and Clay Films in Two Michigan Hydrosequences
Authors: Cremeens D. L. , Mokma D. L. 
Published: July 2010

AbstractFine clays (<0.2 µm) from the matrices and clay films of soils from two Michigan hydrosequences were analyzed by x‐ray diffraction to determine depth distributions and relationships to weathering and translocation processes associated with position in the hydrosequence. Illite contents of matrices generally increased, whereas vermiculite decreased with depth. This depth function was most prominent in the well and moderately well drained soils and diminished with decreasing natural drainage. Vermiculite content was negligible in both, and smectite was found in only one of the two poorly drained soils. Clay films from the well and moderately well drained soils had a mixed mineralogy of illite, kaolinite, and vermiculite, whereas those from the somewhat‐poorly drained soils were primarily illitic. Where present, clay films from the poorly drained soils contained smectite in addition to illite and kaolinite. Depth distributions of matrix clay minerals in the better drained soils suggested that illite had weathered to vermiculite and hydroxy‐interlayered vermiculite. Prolonged saturation and associated higher pH values may have favored illite‐smectite transformations in the poorly drained positions. We suggest that hydrosequence differences in moisture content of the eluvial zones resulted in a differential dispersion of clay minerals upon wetting. This may have led to selective translocation and the observed differences in clay film mineralogy.
Forest Floor Dynamics in Even‐Aged Northern Hardwood Stands
Authors: Snyder K. E. , Harter R. D. 
Published: July 2010

AbstractForest floor beneath three even‐aged pin cherry (Prunus pensylvanica L.)‐birch (Betula alleghaniensis Britton and B. papyrifera Marsh.) stands were analyzed for concentrations of Ca, Mg, K, N, P, C, and total forest floor mass. A 93‐yr‐old even‐aged northern hardwood stand served as the preharvest comparison. A trend of net forest floor material loss continued beyond canopy closure, with the Oa horizon being responsible for the change. Nutrient concentrations did not change in the Oi horizon over time. The Oe showed a peak Ca concentration at 30 yr of more than two and one‐half times that of the younger and preharvest stands. Nitrogen concentration decreased in the Oe horizon and the C/N ratio widened at 10 yr. The Oa horizon had no change in Ca or Mg, but K and N increased significantly in the 10‐ and 30‐yr stands.
Simple Kinetic Fractionation of Reactive Aluminum in Soil “Solutions”
Authors: Bartlett Richmond J. , Ross Donald S. , Magdoff Fred R. 
Published: July 2010

AbstractA method is described that measure empirically the highly reactive portion of Al in 50 to 1000‐uL soil “solution” samples such as those removed from field moist soil by pressure, centrifuging, immiscible displacement, or lysimetry. Three categories of Al reactivity are identified in a single sample: rapidly reacting (RR Al), moderately rapid (MR Al), and total reactive Al (TR Al). Compared with other operational kinetic methods for labile Al, this method is applicable to small samples and is quick, simple, and precise because measurement is integrated over a period of minutes rather than confined to a single time point observation. Correcting for Fe interference does not require reduction and complexation procedures that alter Al speciation. Because of its sensitivity to very small changes in reactivity of Al, this method should be useful for the experimental evaluation of possible increases in mobility of biologically active soil Al, such as those hypothesized to be induced by acid precipitation.
Enhanced Phosphorus Status of Maize Resulting from Nitrogen Fertilization of High Phosphorus Soils
Authors: Kamprath E. J. 
Published: July 2010

AbstractShort‐term greenhouse and culture solution studies have shown that P uptake and translocation is regulated by N. The objective of this study was to determine the effect of N rate on P status of corn (Zea mays L.) grown on soils with varying levels of available P in the range adequate for growth. Field experiments were conducted on Dothan (Plinthic Paleudults), Goldsboro (Aquic Paleudults), and Portsmouth (Typic Umbraquults) soils. Nitrogen rates used were 0, 56, 112, 168, and 224 kg N ha−1 supplied as NH4NO3 and urea. Phosphorus was applied at a rate of 22 kg P ha−1. Leaf P concentration at silking was increased by N fertilization and was highly correlated with leaf N concentration. Total Paccumulation was highly correlated with total N accumulation. Available soil P levels had little effect on leaf P concentration and total P accumulation. Nitrogen supply was the main factor affecting the P content of corn on soils with adequate levels of available P.
Relative Availabilities of Native, Residual, and Fertilizer Phosphorus to Winter Wheat
Authors: Sharpley A. N. 
Published: July 2010

AbstractThe uptake of fertilizer P by winter wheat (Triticum aestivum L.) was investigated for four Southern Plains soils in 900‐cm2 field plots over 4 yr, to quantify the relative availability and uptake of native, fertilizer, and residual fertilizer P. Statistically significant differences between duplicated treatments were determined by analysis of variance. Winter wheat was harvested 70 d after the September planting. At this time the proportion of soil Bray P from native and residual P increased (3.7‐ to 4.6‐fold) with successive annual fertilizer P applications (30 kg P ha−1 yr−1), while that from fertilizer P remained fairly constant. The uptake of winter wheat P from native and residual P increased and from fertilizer P decreased with successive fertilizer applications, due to an increasing amount of residual P uptake. Residual fertilizer P uptake by winter wheat was distinguished from native soil P and quantified as the difference in uptake determined by nonisotopic and isotopic methods. The nonisotopic method represents the difference in uptake between check and fertilizer P treatments, which will include fertilizer and residual P uptake, whereas the isotopic method represents only fertilizer P uptake. It was thus calculated that uptake of residual fertilizer P increased annually, representing from 4 to 40% of P uptake by winter wheat at harvest. By comparing the amount of wheat P from soil and fertilizer, it was found that the relative availability of native and fertilizer P did not change with continued fertilizer application to the four soils.
Application of a Modified Langmuir Isotherm to Phosphate Sorption by some Acid Soils
Authors: Kuo S. 
Published: July 2010

AbstractPhosphate sorption by 11 acid soils was conducted at 298 K and at a pH of about 6.0 to determine how well the sorption can be described by a modified Langmuir isotherm. The modified Langmuir isotherm, which takes into consideration the electrostatic interaction among the phosphate surface species, described the sorption data reasonably well. The average affinity constant for the soils was 1.82 × 104 L mol−1, and the energy derived from the interaction component averaged 1.42 RT, where R is a gas constant and T is absolute temperature. The affinity constant was significantly affected by the amorphous Al and Fe contents of the soils, but no significant relationship between the interaction energy and the clay, organic matter, and amorphous Al and Fe contents of the soils was observed. Although the classical Langmuir isotherm slightly overestimated or underestimated the affinity constant, depending on which linearized form was used, it considerably underestimated the capacity of the soils to sorb phosphate particularly at higher phosphate concentrations. A simplified equation was developed based on the modified Langmuir isotherm, assuming a constant 1 RT contribution from the interaction component. The equation was as simple as that for the classical Langmuir isotherm but provided a better estimate of the sorption capacity of phosphate by soils than did the latter one.
A Unifying Quantitative Analysis of Soil Texture: Improvement of Precision and Extension of Scale
Authors: Shirazi Mostafa A. , Boersma Larry , Hart J. Warren 
Published: July 2010

AbstractThis paper extends a procedure for transforming the standard textural triangle into a new diagram based on mean particle size, dg, and standard deviations of particle size, σg. Values of dg and σg, obtained from the mechanical analysis on percents of clay, silt, and sand, provide a unified basis for comparing soils and physical and chemical properties of the soils. It is shown that the procedure proposed earlier is valid for samples that do not have a lognormal distribution for the whole sample. Using this approach, samples with very different distributions of each fraction can be accurately described. Information from different classification systems (e.g., USDA, ISSS, and engineering) can be used to calculate dg and σg, thus making it possible to unify the systems. The procedure further makes it possible to extend the scale to include particles with diameters > 2 mm. Mean particle size and standard deviates are correlated with soil properties. An application is shown in the from of a relationship between water retention and dg and σg.
Evaluation of Relationships Between Oak Site Indices and Properties of Selected Dystrochrepts
Authors: Edmonds W. J. , Rector D. D. , Wilson N. O. , Arnold T. L. 
Published: July 2010

AbstractSoils derived from argillaceous rocks in the Blue Ridge and Valley and Ridge in Virginia have been mapped and correlated as members of Typic (Berks) and Lithic (Weikert) Dystrochrepts. SCS‐SOI‐5 interpretation records show soils of the Berks series to have higher estimated upland oak site indices than soils of the Weikert series. To explain observed differences in distributions of upland oak site indices, distributions of 34 soil and site properties were evaluated. According to the Shapiro‐Wilk test, the majority of these properties had nonnormal distributions. Therefore, α levels associated with the parametric, two‐sample t‐test would be unreliable. The nonparametric Wilcoxon rank sum test is distribution free and provides reliable α levels for small samples with nonnormal distributions if the samples have similar dispersions. According to the Moses ranklike test, only available water capacity (AH2O) had significantly different (p = 0.05) dispersions for Typic and Lithic Dystrochrepts. Typic Dystrochrepts had significantly larger (p = 0.05) median values for depths to C and R horizons, AH2O, and AL3+ saturation of the cation exchange capacity (CEC). Lithic Dystrochrepts had significantly larger median values for exchangeable Ca2+, total exchangeable bases, CEC, pH‐dependent charge, exchange acidity, ratio of the CEC to clay, and feldspar. Observed median values for upland oak site indices of 56 and 52 for Lithic and Typic Dystrochrepts, respectively, were not significantly different. Significantly larger amounts of feldspar and exchangeable bases, especially Ca2+, and significantly lesser amounts of exchangeable Al3+ saturation of the CEC of Lithic Dystrochrepts are hypothesized as reasons for their slightly higher upland oak site indices. Significantly larger amounts of exchange acidity in Lithic Dystrochrepts are the result of larger amounts of pH‐dependent charge and probably do not adversely influence tree growth. The simultaneous consideration of selected combinations of these properties using discriminant analysis does not produce mutually‐exclusive groups or groups that correspond to limits defined for Lithic and Typic Dystrochrepts. Only the limit of 50 cm depth to bedrock produces classes that correspond to these subgroups.
Polymer Type and Water Quality Effects on Soil Dispersion
Authors: Helalia Awad M. , Letey J. 
Published: July 2010

AbstractTen polyacrylamide (PAM) and derivatized guar compounds, with different charges were tested at 0, 10, and 50 mg L−1 concentration with low electrolyte solution (1 molc m−3) at 0, 5, and 20 sodium absorption ratio values for their ability to reduce dispersion of three soils. Dispersion was determined by measuring the soil settling rate in solution. All compounds were effective in promoting clay flocculation at a concentration of 10 mg L−1. When compared at comparable charge, the PAM compounds were more effective than the guar compounds. This result is consistent with their higher molecular weight. The order of effectiveness of the compounds was cationic > nonionic > anionic. No cationic PAM compounds were available and the cationic guar compound (CP‐14) was comparable to the nonionic PAM. Flocculation decreased very slightly as the SAR increased, suggesting that the effect of low electrolyte concentration was the prominent factor in dispersion. The cationic guar “CP‐14” was tested separately with low (0.05 dS m−1) and moderate (0.7 dS m−1) electrolyte concentrations simulating canal and well waters from California. Its effect on flocculation was very high at 5 mg L−1 concentration in both waters after only 10‐min settling. Increasing the concentration >10 mg L−1 did not improve the flocculation results.
Effects of Low Ionic Strength Solutions on pH of Acid Forested Soils
Authors: Richter D. D. , Comer P. J. , King K. S. , Sawin H. S. , Wright D. S. 
Published: July 2010

Abstract“Salt effects” on soil pH are not well‐documented with highly acidic soils in contact with solutions of very low ionic strength (< 1 mMc/L). These dilute, acidic conditions are typical of soil solutions in many forest ecosystems. A wide range of acid forested soils were contacted with very dilute salt solutions to determine effects of low electrolyte concentrations on soil and solution pH under a variety of experimental conditions. In many soils, pH was lowered markedly following addition of dilute salt solutions. In fact, salt effects on pH (i.e., dpH) were greatest at low concentrations of added salts (e.g., between 0 and 0.6 mMc/L of added salt solutions). At least 40% of the variation in dpH among the 19 mineral soils was attributable to soil differences in low‐level concentrations of water soluble electrolytes. Leaching experiments that manipulated electrolytes in soil solution demonstrated that pH could be depressed up to 1 pH‐unit by increasing salt concentrations by as little as 0.3 mMc/L. Significant correlations between low ionic strength and dpH indicated that water‐soluble electrolytes influence pHw, even of unfertilized, acid soils that are very low in concentrations of soluble ions. Measuring pH of forest soils with 0.01 M CaCl2 is thus preferable to such measurements with water, to mask variations in soil pH that are caused by variations in relatively low concentrations of water‐soluble electrolytes. Results support the contention that variations in electrolyte concentrations in soil solutions on the order of 0.1 to 0.5 mMc/L (due to natural causes or “acid rain”) affect soil‐solution pH, although probably by relatively minor amounts in many or most soils.
Phosphate Adsorption by Two Highly‐weathered Soils
Authors: Mehadi Ahmed A. , Taylor Robert W. 
Published: July 2010

AbstractPhosphorus adsorption by two highly‐weathered soils, Decatur clay loam (clayey, kaolinitic, thermic, Rhodic Paleudult) and Hartsells sandy loam [fine‐loamy, siliceous, thermic, Typic Hapludult] from northern Alabama was studied. Virgin and cultivated soils were used and adsorption curves developed at 15 and 25 °C. From these data the isosteric heat of adsorption (), the Langmuir adsorption maximum (b), and binding constant (K) were calculated. The virgin soils which had lower pHs and higher exchangeable Al and free Fe oxide, adsorbed more P than the cultivated soils. At the higher temperature, P adsorption (x/m) and K increased, indicating that P adsorption was an endothermic process and suggesting that P was held more tightly to the surface. Generally virgin soils had higher than the corresponding cultivated soils in agreement with the calculated K for the soils. decreased with an increase in surface coverage, finally levelling‐off for all soils which gave curvilinear (two slope) Langmuir plots. For the Hartsells cultivated soil, however, was almost constant and a near perfect fit of the linear form of the Langmuir equation was obtained. This suggested that, in this soil, P was adsorbed basically with one energy of adsorption and may explain the good fit to the linear Langmuir equation. The curvilinear lines gave straight lines when plotted according to the Brunauer‐Emmett‐Teller (BET) equation. We speculate that P adsorpation by the soils may be described by at least two previously hypothesized mechanisms of adsorption.
Enzymatic Coupling of 2,4‐Dichlorophenol to Stream Fulvic Acid in the Presence of Oxidoreductases
Authors: Sarkar Jawed M. , Bollag Jean‐Marc , Malcolm Ronald L. 
Published: July 2010

AbstractThe coupling of 14C‐ring‐labelled 2,4‐dichlorophenol (2,4‐DCP) to stream fulvic acid was investigated in the presence of several oxidoreductases including tyrosinase, peroxidase, and laccases of Rhizoctonia praticola and Trametes versicolor. During 12‐h incubation of each of the oxidoreductases with 14C‐2, 4‐DCP and stream fulvic acid, a substantial amount of the radioactivity was incorporated into fulvic acid. Chromatographic analyses indicated that although a large portion of the radioactivity remained in solution, no unbound 14C‐2,4‐DCP was present in the supernatant. The effects of pH, temperature, concentration of fulvic acid, and concentration of enzyme on the coupling processes were studied. The results of this research provide evidence that the enzymatic coupling of certain xenobiotic pollutants to humic substances is an important natural process which must be considered in studies of the fate, reactivity, and persistence of these organic compounds in soils and stream waters.
Micromorphological and Physico‐chemical Characteristics of Soil Crust Types in Northwestern Alberta, Canada
Authors: Arshad M. A. , Mermut A. R. 
Published: July 2010

AbstractThe micromorphology and submicroscopy of naturally‐formed surface crusts in several soils from the Peace River region, alberta were studied in order to understand the types and mechanisms of crust formation. Although the soils studied contained stable aggregates in the dry state, these aggregates almost completely broke down when wet, leading to the crusting tendency of the soils. Other soil characteristics that likely induced the structural deterioration were high silt contents, exchangeable Na and Mg, and low organic matter contents. Three morphological types of surface crusts were identified, including (i) lamellar, (ii) sedimentational, and (iii) disruptional. Lamellar crusts were typical of soils high in clay and exchangeable Na and Mg. Sedimentational crusts were found in areas which were subject to large amounts of surface runoff and subsequent sedimentation of suspended materials. Disruptional crusts were formed by direct raindrop detachment of soil aggregates, subsequent disruption of aggregates, and a reduction of volume within the crust. Disruptional crust was the most common crust formed in the silty soils of the Peace River region. One characteristic, very common to all crust types, was the presence of 2 to 5 µm thick layers within the immediate surface that caused the complete sealing of the soil surface. The moisture content of the immediate surface layer determines the strength of the crust. Hence, water management and mulching is crucial for crust prone soils.