bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Descriptive Model of Soil Test Nutrient Levels Following Fertilization
Authors: Cox F. R. , Kamprath E. J. , McCollum R. E. 
Published: July 2010

AbstractFor efficient utilization of fertilizer, a practical means of expressing the residual effect of certain plant nutrients is needed. A descriptive model was developed to show the change in extractable nutrient levels with time assuming a rapid increase after fertilization followed by a slower exponential decrease. The information needed or parameters for the model include (i) the equilibrium soil test level, (ii) the magnitude of the initial sorption reaction, and (iii) a loss constant. These were determined for seven long‐term fertilizer studies with phosphorus (P). There was a large difference in P‐sorption capacity of the soils; all parameters reflected this difference. The initial sorption reaction was linearly related to rate of fertilization in some soils and quadratically in others. The model was applied to conditions in which fertilizer was applied at various time intervals. Good agreement between observed and predicted values was obtained. The main value of this model is to be able to calculate the amount of fertilizer needed to establish and maintain a given soil test level.
Increasing Sensitivity of Organic Matter and Nitrogen Analysis Using Soil Separates
Authors: Tan K. H. , Troth P. S. 
Published: July 2010

AbstractLittle is known about the use of soil separates in the determination of soil organic matter and total‐N content. To achieve uniformity and complete oxidation, soil samples for use in these analyses are commonly finely ground. The present investigation was initiated to study organic matter and total‐N contents in sand (2.0‐0.050 mm), silt (0.050‐0.002 mm), and clay (< 0.002 mm) fractions of selected Alfisols, Aridisols, Entisols, Mollisols, Spodosols, Ultisols, and Vertisols. A further aspect of this study was to establish the correlation with the respective contents obtained by analysis of whole soil (< 2 mm) samples. Soil organic carbon was determined by the Walkley‐Black wet oxidation method, while total‐N was analyzed by the semi‐micro Kjeldahl method. All analyses were done in four replications. The results indicated that particle size separation had concentrated most of the organic matter in the soil fraction < 2 µm. Generally lower amounts of organic C and N were detected in the silt and sand fractions. In most cases, summation of organic C and total‐N percentages derived from soil separates yielded values higher than those obtained from analyses of whole soils, indicating that, by the use of whole soils, a considerable part of C and N was not analyzed. The higher‐organic C contents in clay fractions, exceeding in a number of cases those measured by the use of whole soils, and the detection of appreciable amounts of organic C and N in silt and sand, pointed to a more complete oxidation and better sample uniformity. The higher recovery of organic C by the use of soil separates also implied an increase in sensitivity of the analysis, improving reliability of results, which was of special importance with B horizon samples, where low levels of organic C were involved. The usual positive correlation between organic C and total‐N content was also obtained by using soil separates. The high correlation (r = 0.929, df = 23), together with increased sensitivity and complete oxidation resulting in higher values and improved reliability, makes the use of soil separates desirable in organic C and total‐N analyses.
Distinguishing the Forest Floors of Three Ecosystems
Authors: Quesnel H. J. , Lavkulich L. M. 
Published: July 2010

AbstractForest floor classifications have been based on morphological properties which were perceived to reflect genesis. These classification systems have not been compatible with soil or ecological classifications, which may have limited their application to forest management. Three biogeocoenoses or ecosystem types near Port Hardy, British Columbia were selected for studying forest floor properties. The sites chosen represent xeric, mesic, and hygric positions along a hygrotopic gradient. The forest floor of each site was stratified into LF(01) and H(02) horizons. A stratified random sampling procedure was used to collect 15 samples within the horizon units of each site. Forty variables were measured or calculated for each sample.A two‐way analysis of variance in conjunction with the Student‐Newman‐Keuls Range Test was used to determine which variables, on an individual basis, would distinguish the forest floors of each site, the LF and H horizons overall, and the individual forest floor horizons of each site. The forest floors of the three sites could be differentiated on the basis of total K, exchangeable Na displaced by 1N NH4OAc, and the ratio of loss on ignition to total C (LOI/C). The LF and H horizons overall could be separated by total K, total Zn, exchangeable Ca and K displaced by 1N NH4OAc, exchangeable K displaced by 1N NaCl, base saturation at pH 7.0, pH measured in water and 0.01M CaCl2, LOI, the ratio of total Ca to total Mg, and the ratio of total Ca to total K. The forest floor horizons of all three sites could not be distinguished by use of single variables. Three stepwise discriminant analyses using nine, five, and two variables yielded classification accuracies of 94.4, 81.1, and 71.1%, respectively, for differentiating the forest floor horizons of all three sites. The multivariate analysis showed that the best combination of measurements for distinguishing the forest floor horizons of the individual sites are total N, total K, total P, LOI/C, and cation exchange capacity (CEC) estimated with 1N NaCl.
Oxidation and Ejection of Nickel and Zinc from Natural and Synthetic Magnetites
Authors: Sidhu P. S. , Gilkes R. J. , Posner A. M. 
Published: July 2010

AbstractAn acid dissolution technique was used to determine the distribution of nickel and zinc in large magnetite crystals and in hematite produced by oxidation of these crystals at high temperatures. About 10% Ni and 17% Zn content of crystals were ejected to the surface by this heating. These are smaller proportions than were observed for microcrystalline synthetic magnetites. The surfaces of partly dissolved crystals contained triangular patterns of etchpits and raised Ni‐rich regions, indicating that dissolution did not occur uniformly.Finely ground natural magnetite altered directly to hematite, whereas synthetic magnetite altered to maghemite at low (ca.200°) temperatures. This difference may be associated with the presence of structural water in synthetic magnetites.
Transformation of Chlorite to Smectite Through Regularly Interstratified Intermediates
Authors: Senkayi A. L. , Dixon J. B. , Hossner L. R. 
Published: July 2010

AbstractTrioctahedral, iron‐rich chlorite separated from east Texas lignite overburden shales by high gradient magnetic separation was characterized by XRD and by IR spectroscopy. The chlorite was then subjected to chemical oxidation by digestion (ca. 100°C) in a saturated bromine solution to simulate weathering. X‐ray diffraction indicated that the chlorite was transformed to smectite through regularly interstratified chloritevermiculite and chlorite‐smectite intermediates. The smectite ultimately dissolved. All of the chlorite reacted in 2 weeks. Electron micrographs of partially weathered particles of chlorite showed thin plates folded at the edges and unreacted cores in the center. Iron released during the reaction tended to precipitate along particle edges. It is postulated that the thin, folded edges and the cores were smectite and chlorite, respectively. Formation of the iron‐rich chlorite in the lignite overburden shales probably resulted from interactions between aluminous smectite and solutions rich in ferrous Fe. Exposure of the overburden shales to oxidizing conditions may result in the transformation of chlorite to smectite with precipitation of released Fe.
A Portable Device for Installing Lightweight Borders for Runoff and Erosion Plots
Authors: Warn W. R. , Allmaras R. R. , Muilenburg G. A. , Zuzel J. F. 
Published: July 2010

AbstractRunoff and soil erosion studies in farm fields in the Pacific Northwest require that borders for runoff and erosion plots be placed after all farm operations are finished just before the winter rainy season. Such an experimental procedure requires a portable, lightweight device to install borders, which are also portable and reusable. A border installation device was developed for easy portage into fields, and use without any vehicular traffic in the field. The device was drawn toward the field boundary using a pickup‐mounted winch. This border system performed as well as galvanized borders. Yet operational costs were less, portability was achieved, and field disturbance was minimal.
Soil Hydraulic Properties as Stochastic Processes: I. An Analysis of Field Spatial Variability
Authors: Russo David , Bresler Eshel 
Published: July 2010

AbstractDeterminations of the sorptivity (S) and five parameters describing the hydraulic conductivity [K(h)] and soil water retentivity [θ(h)] functions have been used to analyze the spatial distribution of the hydraulic properties in an experimental field. The parameters are: saturated hydraulic conductivity (Ks); water entry value (hw); saturated (θs) and residual (θr) water contents; and a constant β characterizing the pore size distribution of the soil. For a given depth, each of these parameters is described as a realization of a stationary two‐dimensional isotropic and random process. These stochastic processes are characterized by truncated normal or log‐normal probability density functions independent of the spatial position, and by autocorrelation functions between any two spatial points in the field which depend solely on the size of the vector separating the two points. The spatial variability of each of the six parameters has a structure that is characterized by a characteristic length—the integral scale, J, representing the largest distance for which the parameter is correlated with itself. Values of J, which are calculated from the autocorrelation functions for each parameter generally decrease with depth. On the average over depth the calculated values of J are 21, 44, 55, 25, 35, and 15 meters for the parameters Ks, hw, θs, θr, S, and β, respectively. The spatial variability of the hydraulic functions are described by the probability density functions and the autocorrelation functions. Since the integral scales of K(h) and θ(h) vary with both h and depth, the characteristic length of the field has been chosen as the integral scale of the weighted mean diffusivity which is 18 m.
Spatial Dependence of Physical Properties of a Typic Torrifluvent Soil
Authors: Gajem Y. M. , Warrick A. W. , Myers D. E. 
Published: July 2010

AbstractThe spatial structure of soil properties has been examined on a Typic Torrifluvent soil at The University of Arizona Experiment Station at Marana. Nine hundred samples from nine transects were collected in straight lines (100 locations for each transect), at 20‐, 200‐, and 2,000‐cm intervals. All samples were at a 50‐cm depth. Variables include 0.1 and 15 bar water content, available water, surface area, particle size distribution, pH, EC, bulk density, and moisture content in the field seven days after irrigation. Autocorrelation functions were evaluated for each parameter and found to be correlated over space with patterns of three basic types: typical, random, or with a large zone of influence. Generalizations were difficult, but the calculated zone of influence was strongly dependent on distance between samples, with larger intervals tending to give greater values. In a few cases, this could partially be explained on the basis of larger standard deviations measured on longer transects. Results indicate future difficulty in assigning scale lengths by parameter or soil.
Effect of Four Continuous Tillage Systems on Mechanical Impedance of a Clay Loam Soil
Authors: Bauder J. W. , Randall G. W. , Swann J. B. 
Published: July 2010

AbstractSoil strength may influence root growth as much as soil bulk density and matric potential. Aerial plant growth and harvestable crop yield have been positively correlated with root growth under some circumstances. Farm machine traffic and tillage practices affect soil strength and mechanical impedance. Most field studies of soil strength, mechanical impedance, root growth, and tillage have been performed on relatively coarsetextured, loamy sand soils. This study was conducted to evaluate the effect of four continuous tillage systems on strength, mechanical impedance, and soil physical properties of a Nicollet clay loam soil, a fine‐loamy, mixed, mesic Aquic Hapludoll.Following 10 years of continuous tillage in a monoculture grain‐corn (Zea mays L.) production system, soil bulk density (ρ), porosity (ε), water content (θ), and mechanical resistance (cone index, CI) were measured on four tillage systems. Replicated measurements of ρ, ε, θ, and CI were made as a function of both depth and position relative to the crop row. No attempt was made to distinguish trafficked and nontrafficked interrow areas because of lack of complete traffic control. Tillage systems included (i) fall moldboard plow, (ii) fall chisel plow, (iii) spring disk, and (iv) no tillage‐slot plant.Tillage treatment, soil depth, and depth by position interaction were sources of significant variation in CI. Differences in CI due to position relative to crop row were not significant. Significant differences in ρ, ε, and θ were attributed to depth and depth x tillage interaction.Tillage and traffic pans were observed under all tillage systems except chisel plowing. Annual moldboard plowing and chisel plowing in the fall resulted in the least amounts of mechanical resistance. Maximum CI resulted from spring disking practices. Mechanical impedance following continuous no tillage was similar in distributional pattern to the spring disking system, although CI following no tillage was not as great. Continuous no tillage and spring disking resulted in pronounced increases in CI close to the soil surface (0–7.5 cm). These increases in CI were attributed to tillage, traffic pans, or to both. These zones of increased mechanical resistance may potentially be root‐restricting layers.Increased emphasis on reduced and no tillage systems of seedbed preparation and monoculture production systems may lead to an increase in root‐restricting tillage pans in clay loam soils. If increased root growth is necessary to insure an adequate supply of water and nutrients, then periodic, relatively deep chisel or moldboard plowing may be necessary to eliminate or modify shallow tillage‐ and traffic‐induced pans that could potentially restrict root growth.
Saturated Flow Above a Terraced Barrier
Authors: Prunty Lyle 
Published: July 2010

AbstractSteady‐state saturated flow through a permeable surface layer of uniform depth (verticle thickness) overlying a terraced barrier has been analyzed by the Gram‐Schmidt method. The geometry and boundry condition concepts of the problem originated in the reclamation of a surface mine where, after reclamation, a soil layer of relatively high permeability overlies impermeable spoil. The soil surface and the soil‐spoil interface both have a terraced contour, and the soil is of uniform thickness. The terraces consist of a series of level benches, each approximately 4 m higher in elevation than the next lower terrace. The terraces are joined by 10 m of 40% slope. The soil is 3 m in depth and it is assumed to be saturated.A new iterative technique involving separating the flow region of concern into two overlapping regions is used to solve the problem. The results show a significant water flow in the soil layer only in the sloped region and in the immediately adjacent region. There is negligible flow in regions where the horizontal distance form the sloped portion of the soil exceeds the soil depth.
Solute Movement in Structured Soils: Two‐Region Model with Small Interaction
Authors: Skopp J. , Gardner W.R. , Tyler E.J. 
Published: July 2010

AbstractA theory of solute movement is presented for those soils where the liquid‐filled pores can be partitioned into two distinct pore size classes. One region represents macro‐ or interaggregate porosity, and the other represents matrix or intraaggregate porosity. The regions may differ in dispersion coefficient, porosity, and flow velocity. In addition, an interaction coefficient characterizes the linear transfer between regions. A regular perturbation method is used to solve the model equations for small interaction coefficients. It is shown that if the interaction coefficient is large, the model approaches the classical dispersion equation. Esitmates of the interaction and its dependence on flow rate are presented along with the influence of interaction on the shape of the breakthrough curves.
Effect of Pyrophosphate on Orthophosphate Reactions in Calcareous Soils
Authors: Amer Fathi , Mostafa H. E. 
Published: July 2010

AbstractSodium pyrophosphate (NaPP) is known as a crystal growth inhibitor. Its effect on the kinetics of phosphorus (P) retention by calcium carbonate (CaCO3) and by two calcareous soils was investigated using orthophosphate (OP) solutions ranging in P concentration between 0.1 and 1 × 10−3M. Reaction of the most dilute solution with CaCO3 involved initial rapid adsorption of P followed by a gradual change in solution composition toward equilibration with hydroxyapatite (HAP). For the more concentrated solutions, the P concentration vs. time curves exhibited an initial, rapid adsorption followed by an induction period that preceded a second drop which was proportional to the initial concentration, and finally a gradual decrease toward a solubility equilibrium value. Amounts of P removed during the initial drop were close to the calculated Langmuir adsorption maximum. The second drop in P concentration was presumed to reflect precipitation involving growth of calcium phosphate nuclei adsorbed on the CaCO3 surface. Behavior of a desert soil (39% CaCO3) was quite similar to that of CaCO3, while the precipitation reaction was considerably less in an alluvial soil (4.1% CaCO3).Addition of NaPP at a concentration of at least 2 × 10−5M P increased both the induction period and the final P concentration. Effectiveness of NaPP depended on its addition before the end of the induction period as well as on the pyrophosphate‐to‐orthophosphate ratio. Results obtained with triammonium pyrophosphate on the two soils were similar to those with NaPP.
Reduction and Reoxidation Cycles of Manganese and Iron in Flooded Soil and in Water Solution
Authors: Patrick W. H. , Henderson R. E. 
Published: July 2010

AbstractCycles of manganese (Mn) and iron (Fe) reduction and reoxidation were examined in suspensions of Crowley silt loam (a thermic Typic Albaqualf) and in water solutions. In stirred soil suspensions at a constant pH of 7.0, the redox potential was varied stepwise from reducing conditions to oxidizing conditions and then stepwise back to reducing conditions. For 50‐mV incremental changes in redox potential, similar redox potential‐pH curves were obtained for the oxidizing half of the cycle and for the reducing half of the cycle when a 2‐week incubation period at each controlled redox potential was used. A 1‐week incubation period did not result in completion of the oxidation and/or reduction reactions, and the curves obtained during oxidation did not coincide well with those obtained during reduction.For soil‐free water solutions, the solubility of Mn was governed almost completely by pH with little effect of redox potential being evident. Iron reduction and reoxidation in water solutions were more sensitive to redox potential, especially at pH 5.0 and at pH 6.0. At pH 4.0, Fe remained in solution at all redox potentials. At pH 7.0 and 8.0, little Fe was present as soluble Fe2+ when the redox potential was decreased.
Seasonal Patterns of Growth and Soil Nitrogen Uptake by Rice
Authors: Moore P. A. , Gilmour J. T. , Wells B. R. 
Published: July 2010

AbstractIn order to model growth and nitrogen (N) uptake by the rice plant as well as improve nitrogen fertilizer management, a description of the temporal behavior of nitrogen in a flooded soil cropped to rice is needed. The objective of this study was to characterize the seasonal changes in soil, water, and plant nitrogen in a flooded rice culture. Lebonnet rice (Oryza sativa L.), a short‐season variety, was grown on a Crowley silt loam soil (a fine, montmorillonitic, thermic Typic Albaqualf). Twelve plots were established utilizing a randomized complete block design with six controls, and six receiving 130 kg N/ha as urea in a three‐way split. Amounts of inorganic soil nitrogen, as well as nitrogen uptake and dry matter production by the different plant fractions, were monitored at weekly intervals for 13 weeks.Nearly 90 % of the preflood application and 95 % of all subsequent inorganic N peaks were exchangeable NH4‐N until the flood was removed. Although the preflood nitrogen application was accounted for in the soil, the midseason applications were virtually undetected. An increase in inorganic soil nitrogen occurred later in the season which was thought to be due to the decomposition of rice straw or algae. In the fertilized plants, 35% of the total dry matter production at harvest was found in the dead tissue, with 31% in the active‐vegetative tissue and 34% in the reproductive tissue. Dry matter production for control plants was 23, 34, and 43% of the total, respectively, for the dead, active‐vegetative, and reproductive tissues. Nitrogen concentrations in fertilized plants were significantly higher than controls until after tillering. Active‐vegetative tissues in fertilized and control plants showed decreases in N concentration with time, while reproductive and dead tissue nitrogen concentrations remained relatively constant after the initial sample dates. Patterns of N uptake were similar to dry matter production. Sixty kg of N per hectare accumulated in control plants and 150 kg of N per hectare in fertilized plants. At harvest, 23, 28, and 49% of the total nitrogen uptake was in the active‐vegetative, dead, and reproductive tissues of the fertilized plants, respectively. In control plants at harvest, 25, 16, and 59% of the uptake was in the active‐vegetative, dead, and reproductive tissues, respectively. In a plot of plant N vs. soil N, the efficiency of N fertilizer use was 55% for the preflood fertilizer application. A relationship was found to exist whereby N in the reproductive tissue increased as the inverse of the N in the active‐vegetative tissue increased.
A Trickle Irrigation System for Frequent Application of Nitrogen to Experimental Plots
Authors: Hairston J. E. , Schepers J. S. , Colville W. L. 
Published: July 2010

AbstractThe purpose of this study was to design a trickle irrigation system which could be used for frequent applications of nitrogen (N) to experimental plots. This type of system is not practical on a large scale for field crops but could be useful in determining rates and time intervals applicable on a much larger scale for specific soils. Two distribution patterns were compared, and a free‐cycling manifold system used in 1976 proved to be superior. Most field research is not conducted on perfectly level land and, according to this study, a free‐cycling manifold system is essential to minimize the effects of hydraulic pressure differences between various plots, rows within plots, or both, at different elevations. Nitrogen distribution is otherwise too erratic to produce statistically different results among treatments.