bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reacidification of Two Lime Amended Soils in Western Oregon
Authors: Doerge Thomas A. , Gardner E. Hugh 
Published: July 2010

AbstractLeaching of basic cations by winter rainfall and irrigation water and the increasing use of NH+4‐fertilizers have resulted in wide‐spread soil acidity in western Oregon. While applications of liming materials are often made in this region, the rates at which limed soils reacidify are generally not known. The objectives of this study were to: (i) quantify long‐term acidification rates of two lime‐amended soils in western Oregon, and (ii) identify soil‐plant processes which may control acidification rates. Lime applications ranging from 0 to 14 650 kg ha−1 were made on a Nekia sicl (Xeric Haplohumults, initial pH 5.0) and from 0 to 11 200 kg ha−1 on a Woodburn sil (Aquultic Argixerolls, pH 5.3) in the Willamette Valley of western Oregon in 1971 to 72. Monitoring of soil pH and levels of extractable basic cations applied in the liming materials for 11 to 12 yr permitted estimation of the rate of acidification of soils receiving different amounts of lime. Whether estimated by declines in pH or extractable basic cations, soil acidification rates increased with increasing quantities of lime initially applied. Acidification rates of unlimed Nekia soil were 0.025 pH units yr−1 and 0.17 cmol(+) Ca2+ + Mg2+ kg−1yr−1 while the unlimed Woodburn soil showed no net acidification. Maximum rates of acidification of 0.09 pH units yr−1 and 0.62 cmol(+) extractable Ca2+ + Mg2+ kg−1yr−1 on the Nekia soil and 0.08 pH units yr−1 and 0.36 cmol(+) extractable Ca2+ kg−1yr−1 on the Woodburn soil were measured on plots receiving the highest amounts of lime. Faster reacidification of soils amended with higher lime rates is explained by the pH dependence of acidifying processes such as nitrification, CO2 release via plant and microbial respiration, mineralization of organic matter and dissociation of organic acids in soil solution. Ca2+ release from mineral weathering appeared to have an important effect on soil pH and extractable Ca2+, particularly in the absence of large inputs of acidifying materials such as NH+4‐fertilizers. Accurate prediction of soil acidfication rates will require additional information concerning the pH dependence of soil acidifying processes, the quantity and composition of seasonal through drainage, and the rates of mineral weathering in soils.
Retention and Transport of Sulfate in a Slightly Acid Forest Soil
Authors: Weaver G. T. , Khanna P. K. , Beese F. 
Published: July 2010

AbstractA shallow slightly acid Terra fusca (Rendolls) soil derived from triassic limestone contains substantial amounts of sulfate. Under high sulfate input, low pH and high salt input this soil can further retain sulfate. Soil chemical data indicate that this soil contains exchangeable Al and H. This finding and the analysis of the equilibrium soil solutions from batch and percolation studies indicate that the retention of sulfate can be described by an equilibrium solid/solution phase of the type Al(OH)SO4 (aluminum hydroxy sulfate). Under similar experimental conditions of solution composition and concentration, Freundlich type adsorption/desorption isotherms and the general solute transport equation can describe the retention and transport of sulfate in this soil.
Ion Diffusion in Soils As Related to Physical and Chemical Properties
Authors: Skogley E. O. , Schaff B. E. 
Published: July 2010

AbstractIon diffusion to plant roots is known to be a major factor influencing availability of certain nutrients in the soil. Diffusion of K+, Ca2+, and Mg2+ from soil to a H‐saturated ion exchange resin sink was measured for 20 agricultural surface soils (18 from Montana and two from Iowa) to investigate the relationship between diffusion and selected chemical and physical soil properties. The soils were moistened to a tension of 0.1 mPa and packed into cylinders to a bulk density of 1.25 Mg m−3. Cylinders were placed in temperature‐controlled chambers at 5 or 30°C and ion diffusion into an ionexchange resin sink was measured after 96 h. Diffusion of K+, Ca2+, and Mg2+ was significantly different between soils and at the two temperatures, and there was a significant soil times temperature interaction. Regression of 41 independent soil physical and chemical characteristics against amount of K+, Ca2+, and Mg2+ in the resin revealed several soil chemical and physical properties that were significantly related to ion diffusion. Values for NH4OAC extractable ions were not as highly correlated to diffusion of these ions as were several other factors.
Kinetics and Mechanisms of Aluminum Adsorption on Kaolinite Using a Two‐site Nonequilibrium Transport Model
Authors: Jardine P. M. , Parker J. C. , Zelazny L. W. 
Published: July 2010

AbstractKinetics of Al adsorption on Ca‐kaolinite at selected concentrations, pH, and column lengths were studied using a miscible displacement technique. Observed breakthrough curves (BTC) for continuous injection of pH 4.3, 0.75 to 7.75 µg mL−1 Al solution were well‐described by a two‐site nonequilibrium transport model which assumes that sorption sites can be divided into two fractions: (1) instantaneous equilibrium sites and (2) sites following first‐order reversible kinetics. Independent verification of the fitted parameter β, related to the fraction of type‐1 equilibrium sites, was possible by assuming negative surface charge sites of kaolinite were in local equilibrium with the solution phase. Confirmation of the fitted parameter R, which is a measure of the total Al adsorbed, was not possible due to the nonsingular nature of the equilibrium adsorption isotherm. First‐order rate coefficients (α) for Al adsorption on kaolinite were unaffected by column length. Effects of influent Al concentration on α were small but suggested that kinetic reaction of Al with kaolinite was not strictly first‐order. Decreasing the pH of influent solution from 4.3 to 4.0, eliminated type‐2 kinetic sites. These effects indicate that kinetic reactions involve Al polymerization on kaolinite while equilibrium reactions reflect Ca‐Al exchange. This scenario is supported by Ca desorption data of the effluent and by potentiometric titrations of effluent solutions.
Transient Microsite Models of Denitrification: II. Model Results
Authors: McConnaughey P. K. , Bouldin D. R. 
Published: July 2010

AbstractSolutions to four models of denitrification are presented. The models are based on four coupled reaction‐diffusion equations, each model describing a different type of reaction term. The equations were solved by standard finite‐difference methods and a boundary tracking technique when needed. For a chosen test problem, the zero‐order model predicted sequential reduction of nitrogenous species, a N2/N2O ratio of 0.17, and relatively high transient NO‐2 levels. The Michaelis‐Menten model with threshold and concentration‐dependent NO‐3 and NO‐2 inhibition of N2O reduction predicted N2/N2O ratios of 19.15 and 6.69, respectively. The competitive inhibition model predicted a N2/N2O ratio of 0.23 and N2 evolution followed N2O. A sensitivity analysis of the Michaelis‐Menten model with concentration‐dependent inhibition showed that the species of gaseous N evolved depended strongly on NO‐3 levels in the soil. N2/N2O ratios were also influenced by O2 fluxes, diffusion coefficients, and diffusion distances that affect anaerobic volume and solute transport. The predicted N2/N2O ratios were less sensitive to the Michaelis‐Menten kinetic parameters Vimax and KiM where i = nitrate, nitrite, or nitrous oxide. The qualitative behavior of gaseous N evolution as a function of nitrate levels, gaseous oxygen concentration, and depth of saturation predicted by the models agrees with data in the literature.
Field Estimation of Phosphate Retention by Andepts
Authors: Alvarado Alfredo , Buol S. W. 
Published: July 2010

AbstractIn an attempt to develop a field method for soil surveyors and field agronomists to rapidly evaluate whether or not a particular site would retain a large amount of applied phosphate, 59 samples of Andepts from Costa Rica and Guatemala were incubated with rates of P, then analyzed. Phosphate retention ranged from 25 to 99% and correlated quite well with ammonium oxalate extractable Al concentration (R2 = 0.56) in a linear model. In samples with <2.4% ammonium oxalate extractable Al, the amount of applied phosphate retained was related even better to this measurement, while at > 2.4% oxalate extractable Al, retention was not influenced appreciably by oxalate extractable Al concentration. Phosphate retention was also correlated with pH in NaF. By the methods used, >90% phosphate retention was predicted by an oxalate extractable Al concentration of >2.4% or a NaF pH of >10.7. A quick test was devised to assess soils with extremely high phosphate retention. The method consisted of adding a few drops of 0.1 mol NaF L−1 to approximately one gram of soil in a spot plate and, after 10 min, checking the pH with two drops of 0.04% thymolphythalein indicator. This technique was found to correctly identify 79% of the samples as having either ≷90% phosphate retention.
Sulfur Fertilization of Winter Wheat Grown on Deep Sandy Soils
Authors: Oates Kenneth M. , Kamprath E. J. 
Published: July 2010

AbstractSurface horizons of sandy Coastal Plain soils of the southeastern United States are low in available SO−24, and crops are often dependent upon adsorbed SO−24 in the B horizon. The objective of this study was to determine the response of winter wheat (Triticum aestivum L.) to sulfur (S) fertilization on three soils which varied in depth to the B horizon; a Wagram soil (Arenic Paleudults) > 50 cm to the B, and two Norfolk soils (Typic Paleudults) 31 and 48 cm to the B. Sulfur rates covered the range from 0 to 90 kg S ha−1. Sources used were CaSO4 · 2H2O, elemental S plus bentonite (Sol‐U‐Sul) and (NH4)2SO4. Measurements were made of S concentration and N/S ratio of plants, root distribution with depth at spike emergence and grain yield at harvest. Yield response to S fertilization was obtained on the Wagram soil and the Norfolk soil in which root growth was restricted by a tillage pan but not on the Norfolk soil with the B horizon at 31 cm. A rate of 20 kg S ha−1 as SO2−4 applied in late February was adequate for optimum response. Sol‐U‐Sul applied in February was not effective. Ammonium sulfate was equally effective as CaSO4. Plants responded to S fertilization where nonfertilized plants had S concentrations of 0.6 g kg−1 dry weight and N/S ratios of 21. Response of wheat to S fertilization depended upon the depth to the B horizon and root distribution in the soil profile. No response to S fertilization was obtained on a Norfolk soil in which there was appreciable root growth in the 30‐ to 45‐cm depth. That depth contained an accumulation of SO2−4. Where root growth was essentially restricted to the top 30 cm of a Norfolk soil in which SO2‐4 accumulation started at the 45‐cm depth there was a large response to S fertilization.
Variance and Scale Influences on Classifying and Interpreting Soil Map Units
Authors: Edmonds W. J. , Baker J. C. , Simpson T. W. 
Published: July 2010

AbstractResidual variance including the variance contributed by sampling and laboratory procedures, by soil profiles within circular 7‐m diam sites, by sites within delineated soil bodies, and by delineated soil bodies within each of three second‐order soil survey map units were evaluated using a nested sampling design. Residual variances were small for base saturation, clay, and free iron and large for pH, quartz in the sand fraction, kaolinite, and gibbsite in the clay fraction, and the oxidic ratio. Naming and interpreting map units using classes based on the dissection of variable with large residual variances will be confounded by the sampling and laboratory procedures. Distributions of variance for the soil properties studied revealed that mutually‐exclusive classes were not delineated by these map units. Shortrange variability in field observable soil properties was not mapped because of the constraint of scale. Therefore, users of soil survey information would be better served by procedures for naming and interpreting map units that describe the content and pattern of occurrence of soils rather than relying on classificational units or soil series defined by limits of taxa in Soil Taxonomy to convey map unit content and interpretations.
Thixotropic Changes in the Stability of Molded Soil Aggregates
Authors: Molope M. B. , Grieve I. C. , Page E. R. 
Published: July 2010

AbstractThixotropic age hardening of clays has long been familiar to civil engineers but its contribution to the stabilization of aggregates produced by cultivation has been little studied. We report changes in stability after simulated cultivation of soil samples from arable and pasture fields. The contribution of biological processes to stabilization was eliminated by sterilization and the effects of the “polysaccharide” fraction of the soil organic matter were removed by periodate oxidation. Thixotropic changes were shown to make a contribution to the age hardening process in both molded and remolded soil aggregates similar in magnitude to the contribution made by biological processes. These changes were reversible and accompanied by soil matric water potential changes. Destruction of the polysaccharide fraction of soil organic matter reduced aggregate stability and removed most of the differences between arable and pasture soils of the same series, but polysaccharides do not appear to contribute to the thixotropic aging process.
Soil Erosion Class and Landscape Position in the North Carolina Piedmont
Authors: Daniels R. B. , Gilliam J. W. , Cassel D. K. , Nelson L. A. 
Published: July 2010

AbstractSoil map units in the North Carolina Piedmont are a complex of interfluves, valley slopes and foot slopes. Specific landscape positions are commonly too small to delineate on 1:15 480 or larger scale maps and most contain areas with varying degress of erosion that cannot be separated at common map scales. Munsell color hues are a good indicator of clay content of the Ap horizon and can be used as a guide to erosion class. Within Cecil map units the clay content of the Ap horizons increases from about 10 to 30% as the Munsell hue shifts from 10YR to 5YR. Within Georgeville map units the clay content of the Ap horizons increase from about 30 to > 40% as the Munsell hues change from 7.5YR to 2.5YR. The distribution of erosion classes within a soil map unit delineation varies with landscape position. Within the Cecil map units there are about equal areas of slight and severe erosion on interfluves. Shoulders and linear valley slopes are moderately to severely eroded whereas head and foot slopes (depositional areas) are usually slightly to moderately eroded. The interrelationships between landscape position and erosion class, and among landscape positions, growing season moisture and crop yield, create difficulty for quantifying the effects of erosion on soil productivity. The close relationship between landscape position and erosion class also suggests that a large variation in the original thickness of the A plus E horizons may have contributed to present distribution of erosion classes. The variability in surface properties within a map unit is not necessarily random but is related to the range of intensities of the processes that have been operating within a local landscape.
Corn Fertility Treatments and the Surface Structure of a Poorly Drained Soil
Authors: Stone J. A. , Allen N. H. E. , Grant C. D. 
Published: July 2010

AbstractFertility treatment effects on annual measurements of bulk density, total porosity, and air‐filled porosity taken from the 0.05‐ to 0.15‐m depth of a Brookston clay loam soil (clayey, mixed, mexic Typic Haplaquolls), inclusive from 1957 to 1982, were evaluated. Additional bulk density, porosity, stability, and penetration resistance measurements were made on samples taken from the 0.05‐ to 0.15‐m and 0.15‐ to 0.25‐m depths in 1983. The treatments were (i) continuous corn (Zea mays L.) with no fertilizer; (ii) continuous corn with 298 kg/ha NH4NO3 annually; (iii) continuous corn as in (ii) plus 672 kg/ha of 5–8.8–16.6 (5–20–20) annually; and (iv) a corn, oats (Avena sativa L.), and alfalfa (Medicago sativa L.) rotation receiving 168 kg/ha of 5–8.8–16.6 (5–20–20) for oats. In general, bulk density increased as total and air‐filled porosities decreased with time for all treatments. However, the rotation treatment had lower bulk densities and higher total porosities than the continuous corn treatments. There were no significant differences in bulk density or porosity among the continuous corn treatments. The 1983 stability and penetration data did not show any meaningful treatment effects. However, the stability data illustrate the weak structure of this soil. Monoculture corn appears to play a minor role in the structural deterioration of this poorly drained, weakly structured soil.
Electron Paramagnetic Resonance of Manganese (II) in Newly Humified Clover Leaves
Authors: Sonbol H. A. , Baverez M. 
Published: July 2010

AbstractClover leaves (Trifolium alexandrium L.) were humified by incubation at 30°C for 60 d. Electron paramagnetic resonance (EPR) and infrared (IR) spectra were recorded during that time. The EPR spectra of the leaves exhibited a hyperfine structure characteristic of Mn(II). The theory of the EPR experiment was discussed and the parameters of the spin Hamiltonian were determined. The A and D values of −265 and 150 Mc s−1 respectively, indicated that Mn(II) was coordinated by six oxygen‐containing functional group ligands in an appreciably distorted octahedron environment.
Characterization of Potassium Uptake and Translocation in Soybeans
Authors: Sallam A. , Scott H. D. , Brewer D. W. , Sojka R. E. 
Published: July 2010

AbstractNutrients taken up by plant roots are translocated and distributed to plant parts in order for the plant to carry on its normal functions. To understand these functions better, we developed a five compartment mathematical model which describes K translocation within soybean [Glycine max (L.) Merrill] plant parts during vegetative and reproductive growth. The instantaneous rate of change of K contents in the five‐compartment soil‐soybean system was described using mass balance equations. The seasonal dry matter accumulation, nutrient concentrations, and nutrient contents of the stems, branches, leaves, and pods were used as inputs into the model to determine the effect of growth stage on uptake and translocation parameters. Among the various plant parts, the maximum K fluxes were in the pods (0.257 g m−2 d−1) followed by the branches (0.191 g m−2 d−1), the stems (0.118 g m−2 d−1), and the leaves (0.108 g m−2 d−1). The maximum fluxes of K for the stems, branches, and leaves were reached at the same time during vegetative growth. In general, K uptake was higher during vegetative than during reproductive growth. The magnitudes of the transport coefficients were variable during the growing season. During vegetative growth the highest K transport coefficient (15.18 g m−2 d−1) was from the stem to the branches indicating that the main transport pathway of K was from the stem to the branch. During reproductive growth the highest transport coefficient (23.26 g m−2 d−1) was from the stem to the pods which means that the major movement of K between plant parts during this time was from the stem to the pod. Transport coefficients of K between the branches and pods were low. These results show that the net fluxes of K in soybeans varies with transport pathway within the plant and with plant age.
Ground Cover Estimates for Seedling Cereal Crops
Authors: Rickman R. W. , Rasmussen Paul E. 
Published: July 2010

AbstractFields sown to winter cereals are often damaged by water erosion. Erosion can be reduced if sufficient green plant or crop residue cover is present over winter. The selection of a planting date that will provide adequate overwinter cover is critical to successful management. This manuscript explains how plant cover can be predicted for any date after planting of a winter cereal from historic air temperature records. Degree‐days accumulated from planting are linearly related to cereal leaf development at 80 to 120 degree‐days per leaf. The lengths of successive leaves provide the radii of successively larger circles which are used as the basic unit for computing field cover. A plant is assumed to uniformly shade the circular area surrounding it. The area of overlap of adjacent circles is assumed to be shaded by the sum of the shading from each circle. Formulas are provided to illustrate the effect of row spacing, seeding rate, leaf size, and plant development rate on the rate and pattern of formation of cover. Comparison of calculated and observed field cover from four different growing seasons demonstrated the need for correcting the calculations for mutual shading of leaves. When mutual shading by leaves of 1% per layer of overlap is used, calculated and observed percent field cover are not different. Historic air temperature records can be used with leaf length values characteristic of a cultivar and specific field management choices to provide the latest seeding date that will provide a desired amount of field cover.
Orthophosphate Solubility Transformations and Availability from Dual Applied Nitrogen and Phosphorus
Authors: Hanson R. L. , Westfall D. G. 
Published: July 2010

AbstractKnife applications of NH+4‐N and P fertilizers into common injection zones (dual N and P) have produced higher crop yields and P absorption than other N and P application methods. Enhanced solubility of the P fertilizer reaction products due to the presence of NH+4 could account, in part, for these crop responses. Greenhouse studies were conducted to characterize P reaction product solubility transformations and P availability in dual N and P injection zones. Treatments were ammonium polyphosphate (APP) + NH4OH (used to simulate anhydrous ammonia), NH4OH or KNO3 + nitrapyrin solutions injected simultaneously (dual N and P application) into four different soils (Aridic Argiustolls, Udic Argiustolls, Mollic Albaqualfs, and Typic Argiborolls). Monocalcium phosphate potentials and NaHCO3 or Bray extractable P were used to characterize P solubility and availability relationships in the injection zones. Dual application of NH4OH plus APP with and without nitrapyrin resulted in increased NaHCO3 or Bray‐extractable P in three of the four soils. The mechanisms that resulted in higher extractable P are concluded to be associated with the high injection zone pH caused by NH4OH applications. The postulated mechanisms are: (i) the initial high (alkaline) pH immediately after dual application allows formation of highly available Ca‐P reaction products as opposed to less available Al‐ and Fe‐P reaction products that exist in slightly acid soils, (ii) then the production of H+ during nitrification increases P solubility as phosphate potentials move up the dicalcium phosphate dihydrate and dicalcium phosphate isotherms, and (iii) this rapidly decreasing pH allows the soluble reaction products to persist which results in higher P availability and solubility for a longer period of time. Inclusion of nitrapyrin (a nitrification inhibitor) prolonged the time of Ca‐P reaction product persistence in the injection zone. Dual KNO3 + APP applications resulted in suppressed P availability, as compared to NH4OH + APP, apparently due to formation of less soluble reaction products. This suppressed P availability could account for the relative ineffectiveness of NO‐3 ‐N in dual application.
A Method for Preparing Small Soil Samples with Specified Bulk Densities and Water Contents
Authors: Stypa M. L. , Mayfield C. I. , Dumbroff E. B. 
Published: July 2010

AbstractA centrifugation procedure is described for producing different degrees of compaction in both wet and dry soils. To ensure uniform distribution of water in the test samples, appropriate quantities of crushed ice are mixed with the oven‐dry soils 24 h prior to the centrifugation step.