bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Improved Woodruff Buffer for Estimation of Lime Requirements
Authors: Brown J. R. , Cisco J. R. 
Published: July 2010

AbstractThe dominant quick‐test method of estimating soil lime requirements in the USA Corn Belt and adjacent area is the Shoemaker, McLean, Pratt (SMP) buffer method. This work was done to compare an improved Woodruff buffer with the SMP buffer to determine which most accurately estimated soil lime requirement. This study used a Ca(OH)2‐CaCl2 soil titration procedure and incubation of soils with finely ground, chemically pure CaCO3 to compare the accuracy of the original Woodruff procedure, the SMP single buffer procedure, and the new Woodruff procedure in estimating the lime requirements of 89 soil samples. The results supported 1961 findings by Ohio workers that the original Woodruff procedure drastically underestimated lime requirements. The results also supported the literature that the SMP procedure underestimates low lime requirements. The SMP tended to overestimate high lime requirements. Based upon the results of this study, the new Woodruff procedure was a better predictor of lime requirements than the SMP procedure.
Using Radar to Investigate Organic Soil Thickness in the Florida Everglades
Authors: Shih S. F. , Doolittle J. A. 
Published: July 2010

AbstractA ground‐penetrating radar (GPR) system consisting of a control unit, power distribution unit, graphic recorder, tape recorder, and an antenna with a center carrier frequency of 120 MHz was used to investigate the Florida Everglades' Agricultural Area (EAA) organic thickness. Seven important factors that affected the results of GPR were the speed of antenna advance, antenna frequency selection, soil depth determination, soil moisture content, resonance problems, triple bands appearance, and data extension. Two sites located in the EAA were chosen to demonstrate the application of GPR techniques. The results showed that the GPR using a 120 MHz antenna was applicable to investigate the thickness of organic soil in the EAA. The deviations between auger boring data and radar image were within 8 cm in 91% of all samples, and within 12 cm in all samples. The correlation coefficient between the boring and the radar depth was 0.84.
Soil Water Variation in Spoil and Undisturbed Sites in North Dakota
Authors: Schroeder S. A. , Bauer A. 
Published: July 2010

AbstractAnalyses of total soil water monitored over a 7‐yr period on reshaped, vegetated spoil and nearby undisturbed grassland sites indicate that little, if any, water percolated beyond the rooting zone (0–122 cm) at either the spoil or undisturbed grassland sites. Total soil water below the rooting zone decreased over time, presumably due to upward movement by unsaturated flow in response to gradients created in the rooting zone by evapotranspiration. The spoil sites contained more total soil water in 1974 than the undisturbed sites but greater evapotranspiration losses at the spoil sites had presumably decreased soil water to a level nearly equal to that of the undisturbed sites by 1981.
Effects of Acid Irrigation on Carbon Dioxide Evolution, Extractable Nitrogen, Phosphorus, and Aluminum in a Deciduous Forest Soil
Authors: Johnson Dale W. , Todd D. E. 
Published: July 2010

AbstractA study was initiated to determine the effects of sulfuric and nitric acid irrigation on CO2 evolution, and N, P, and Al availability in a deciduous forest soil. Irrigation with H2O, H2SO4, or HNO3 at 0.05 mol (p+) m−2 and 0.5 mol (p+) m−2 for 1 yr had no consistent effect on CO2 evolution, soil NH+4, extractable P, or extractable Al in a deciduous forest soil under field conditions. Irrigation with HNO3 caused temporary increases in soil NO‐3, but irrigation with H2SO4 had no effect on soil NO‐3. Nitrogen mineralization and nitrification by aerobic incubation were also unaffected by treatments. Seasonal variations in CO2 evolution, NH+4, and extractable P were pronounced, with peaks in CO2 and NH+4 in June and a peak extractable P in August.
Design of an Optimal Sampling Network for Estimating the Variogram
Authors: Russo David 
Published: July 2010

AbstractKriging techniques for interpolating spatial phenomena have recently been applied by soil scientists to map soil properties in heterogeneous field. A fundamental component of these techniques is the variogram which has to be estimated experimentally. A method to design an optimal sampling network for estimation of the variogram is proposed. Using a constant number of pairs of points (Np) per lag class, the criterion for selecting the location of the sampling points is the uniformity of the values of the lag vector, h, within a given lag class, for each of the lag classes which cover the field domain. For a given sample size, N, the method provides a set of scaling factors which in turn is used to calculate the new locations of the sampling points by an iterative procedure. Using the aforementioned criterion, the best set of the sampling points is selected. Analysis of the results showed that by using the proposed method, the variability of h within a given lag class, as well as the variability of h among the lag classes, was considerably reduced relative to the situation where the original locations were used. The method was found to be sensitive to both N and Np as well as to the initial locations of the points. The effect of the method on the estimation of the variogram was tested using simulated realizations of a two‐dimensional stationary and isotropic field. The results for fifty different realizations showed that the variograms which had been estimated from data generated on the coordinates of the sampling points provided by the method were smoother and fitted the theoretical variograms better than those which were estimated from data generated on the original coordinates of the sampling points. When only the smaller lag classes were considered, the differences between the two sets of the variograms become smaller.
Use of Chelating Resins in Metal Adsorption Studies
Authors: Turner M. A. , Hendrickson L. L. , Corey R. B. 
Published: July 2010

AbstractMetal adsorption characteristics obtained using conventional batch equilibration methods are often of limited use for predicting the behavior of trace metals under natural conditions due to inadequate control of the composition and pH of the equilibrium solution. Much of the existing adsorption data has also been obtained using unrealistically high metal concentrations and in response to total soluble metals rather than unassociated metal ions. These limitations were overcome via the use of chelating resin to establish and maintain constant pH and metal activity in a solution of constant ionic strength and composition. The Cd/Ca ratio of the resin was varied to provide a range of Cd activities (0–1.5 µM) consistent with normal soil solution concentrations when equilibrated with 0.01M Ca(NO3)2. A series of these prepared resin systems were equilibrated with an Fe gel, a muck, and an intact soil to obtain Cd adsorption data in response to Cd activities as low as 10−8M. These resin systems can also be used to describe metal adsorption as a function of ionic metal concentrations in systems containing soluble complexing agents. The resins can provide ionic metal concentrations below the sensitivity of flameless atomic absorption spectrophotometry, and the activity of several trace metals can be maintained by the same resin, thus enabling evaluation of metal competition for adsorption sites. In some cases, the resin system may eliminate the requirement for a complete adsorption isotherm, since metal adsorption can be determined in response to one or more predetermined metal activities.
Assessment of Copper‐Soil Bond Strength by Desorption Kinetics
Authors: Lehmann R. G. , Harter R. D. 
Published: July 2010

AbstractKinetics of copper desorption from the A horizon of Paxton soil was investigated following addition of Cu at the rates of 1.6, 3.9, 6.3, and 7.9 µmol Cu/g soil (100, 250, 400, and 500 µg Cu/g soil). The Cu was allowed to react with the soil for 30 min to 4 d, at which time Na‐citrate was added in a 1:1 Cu/citrate charge ratio. Copper adsorption pH was maintained at 5.6, and desorption occurred at pH 6.0. From the desorption kinetics, it appeared that Cu was initially retained on two types of sites. Up to about 1.6 µmol Cu/g was preferentially retained on high energy sites. If Cu addition exceeded this amount, the excess was retained on low energy sites. Within about 24 h, a portion of the Cu initially bound to low energy sites shifted to sites intermediate in energy between the initially observed low energy and high energy sites.
A Simplified Soil and Plant Phosphorus Model: I. Documentation
Authors: Jones C. A. , Cole C. V. , Sharpley A. N. , Williams J. R. 
Published: July 2010

AbstractThe structure of a simple soil and plant P model designed for use in the Erosion‐Productivity Impact Calculator (EPIC) agriculture management model is described. The model maintains pools of stable, active, and labile inorganic P; fresh organic and stable organic P; and grain, stover and root P. The model has a daily time step, simulates P uptake and transformations in up to ten soil layers of variable thickness, and is sensitive to soil chemical and physical properties, crop P requirements, tillage practice, fertilizer rate, soil temperature, and soil water content. Fertilizer P is added to the labile inorganic P pool which is in rapid equilibrium with the active inorganic P pool. The relative sizes of the labile and active inorganic pools are soil specific and are based on soil classification, texture, and chemical properties. Movement of active inorganic P to the stable inorganic P pool simulates slow adsorption of inorganic P. Crop P uptake from a soil layer is sensitive to crop P demand and the amounts of labile P, soil water, and roots in the layer. Stover and root P are added to the fresh organic P pool upon their death and/or incorporation into the soil. Decomposition of fresh and stable organic matter may result in net immobilization of labile P or net mineralization of organic P.
A Simplified Soil and Plant Phosphorus Model: III. Testing
Authors: Jones C. A. , Sharpley A. N. , Williams J. R. 
Published: July 2010

AbstractTesting of a simplified soil phosphorus model is described. Changes in organic P content of the surface soil due to cultivation are simulated relatively accurately for periods of up to 40 years at several locations in the Great Plains. Simulated changes in organic P contents of the subsoil are smaller than those of the topsoil. Concentrations of soil test P are accurately simulated over periods of up to 20 years with and without fertilizer P applications in several soils. Simulated responses of maize (Zea mays L.) and wheat (Triticum aestivum L.) to soil test P concentrations are similar to those found in three published studies. Fertilizer P required to maintain adequate P fertility is accurately simulated for maize and wheat at several locations in the U.S.
Soil Test Values for Phosphorus, Potassium, and Zinc as Affected by Rate Applied to Corn
Authors: Rehm G. W. , Sorensen R. C. , Wiese R. A. 
Published: July 2010

AbstractThe change in land use of the Nebraska Sandhills from native grassland to intensive production of irrigated corn (Zea mays L.) has provided a unique opportunity for the study of changes in nutrient levels of soils as affected by repeated fertilization. This study was initiated in northeast Nebraska in 1974 and continued through 1978 for the purpose of examining the effects of repeated application of P, K, and Zn on corn yield and changes in soil test values for these nutrients. Soil samples were collected prior to fertilization in 1974 for the purpose of site characterization. Soil samples (0–15 cm) were collected after each growing season where corn was harvested for grain and for silage. At the end of the 1978 growing season, samples were collected from each plot at depths of 0 to 15, 15 to 30, 30 to 60, 60 to 90, and 90 to 120 cm. Routine soil test procedures were used to analyze all samples for P, K, and Zn. Repeated application of fertilizer P and Zn produced rapid yearly increases in the soil test values for each nutrient. Repeated fertilization with K produced increases in soil test values for K but at a slower rate than changes in levels of P and Zn. Method of harvest appeared to have no influence on the soil test values for P and Zn. Average soil test values for K were lower when corn was repeatedly harvested for silage. Although relatively high rates were applied, there was no apparent movement of either P or Zn below the tillage zone. Repeated application of K produced increases in soil test values for K at depths as low as 120 cm.
Effects of Artificial Desurfacing on Alfisols and Ultisols in Southern Nigeria: II. Changes in Soil Physical Properties
Authors: Mbagwu J. S. C. , Lal R. , Scott T. W. 
Published: July 2010

AbstractChanges in soil physical properties of two Alfisols and an Ultisol in southern Nigeria as affected by desurfacing to simulate varying levels of soil erosion were monitored for two consecutive seasons (3 and 7 months after exposure). These investigations were conducted at Ilora (Alfisol), Ikenne (Alfisol), and Onne (Ultisol) in southern Nigeria. All measurements were made on the top 5 cm of the undisturbed control and the desurfaced soils. Following topsoil removal some deleterious changes in soil physical properties occurred on the exposed subsoils. Seven months after removal of 10 cm of topsoil, bulk densities had increased from 1.37 to 1.45 Mg m−3 at Onne, 1.23 to 1.50 Mg m−3 at Ikenne, and 1.27 to 1.42 Mg m−3 at Ilora. These increased bulk densities were reflected in decreased total and macroporosities. Seven months after 10 cm of topsoil removal, total porosity was reduced from 48 to 45% at Onne, 52 to 43% at Ikenne, and 52 to 46% at Ilora. Available water‐holding capacities of the surface 5 cm of exposed subsoils following 5 cm of topsoil removal were reduced during 7 months by 61% at Onne, 23% at Ikenne, and 12% at Ilora. Corresponding reductions in saturated hydraulic conductivities of these soils were 75%, 65%, and 35% three months after exposure. Also reduced were the moisture retention at 0.01 MPa suction, and the clay contents of the exposed subsoils. Generally, the magnitude of these changes in physical properties was less for the undisturbed control than for the desurfaced soils. These results strengthen the argument that these structurally unstable soils of the tropics should be managed extremely carefully.
Influence of Field Environment and Fertilizer Management on Ammonia Loss from Flooded Rice
Authors: Fillery I. R. P. , Simpson J. R. , De Datta S. K. 
Published: July 2010

AbstractThe importance of ammonia volatilization after urea application to flooded rice (Oryza sativa L.) was assessed in six experiments at two field locations in the Philippines, using a nondisturbing micrometeorological technique. Earlier studies had produced conflicting results probably because the techniques used did not conserve the balance of physical, chemical, and biological processes that affect ammonia loss in this ecosystem. Urea was either broadcast and incorporated immediately before transplanting of rice seedlings (BI treatments) or broadcast into the floodwater 14 or 21 d after transplanting (AT treatments) and 5 to 7 d before panicle initiation (PI treatments). Ammonia volatilization proceeded rapidly and continued for 6 to 10 d after urea was applied. In the AT treatments, NH3 loss accounted for 47% and 27% of the urea‐N applied. Ammonia loss showed pronounced diurnal fluctuations that were synchronized with fluctuations in floodwater pH, between maxima of 8.6 to 9.0 at 1200 to 1400 h and minima of 7.8 to 8.0 at 0500 to 0600 h in the AT experiments. Floodwater pH in nonfertilized areas showed similar trends, indicating that fertilizer addition was not the prime cause of the pH fluctuations. Ammoniacal N in the floodwater accumulated to ≃ 14 g m−3 in the AT studies, but the concentrations decreased during daytime and increased again at night, with a net loss of ammonia during the day. Differences in wind speed appeared to account for most of the difference in NH3 loss observed between the AT treatments. Rates of ammonia loss (10–15%) were lower when urea was applied at a later growth stage (PI), even though floodwater ammoniacal N again rose to 13 g m−3. In contrast to the AT studies, floodwater pH at PI did not exceed 8.0 to 8.3. Apparently, shading of the floodwater by the rice canopy lowered the photosynthetic activity of the aquatic biomass and thus reduced the degree of CO2 depletion and the potential for NH3 loss. Ammonia volatilization loss after urea incorporation (BI treatment) accounted for only 13% of the N applied at Los Baños. This sharp reduction in loss, compared with those after AT applications, was largely due to lower floodwater urea and ammoniacal N concentrations from 2 days after application in a system where urea was largely incorporated into the soil.
Ammonia Volatilization from Urea and Urea Phosphates in Calcareous Soils
Authors: Stumpe J. M. , Vlek P.L.G. , Lindsay W. L. 
Published: July 2010

AbstractAmmonia volatilization from urea is a considerable problem if fertilizer is surface applied, whether by choice (minimum tillage) or by lack of implements, which is common in the tropics. Urea phosphate [CO(NH2)2·H3PO4] was tested in several experiments as a means of reducing ammonia volatilization losses. Incubation experiments using 15N‐labeled urea were conducted to evaluate ammonia loss from urea, urea phosphate, and urea‐urea phosphate mixtures (N content = 460, 190, 370, and 350 g kg−1, respectively), applied at rates up to 100 kg N ha−1 to a variety of soils using a range of initial moisture contents. Evolved ammonia was measured by collection in an external acid trap. Ammonia volatilization losses from surface‐applied urea ranged from 10% to 30% of that applied, dependent on soil type. Initial soil moisture affected the timing of N loss, but not the total amount. Addition of urea with phosphate (190 g N kg−1) slightly decreased ammonia loss from 17.0% to 12.2% of the applied N on a highly calcareous (225 g CaCO3 kg−1) Mollisols. On the other hand, NH3 losses from a slightly calcareous (20 g CaCO3 kg−1) Vertisols were 10.5% and 3.1%, and from a slightly calcareous Entisols (2.6 g CaCO3 kg−1) were 14.4% and 4.4% of the applied N for urea and urea phospate, respectively. The relative savings of urea‐N were much higher in low CaCO3 soils (approximately 70%) than in the highly calcareous soil (approximately 30%). Mixtures of urea and urea phosphate were substantially less effective in reducing ammonia volatilization with relative reductions ranging from 0% to 20%. Detailed studies of the mobility and reactions of urea phosphate in soils revealed that rapid precipitation of calcium phosphates near the placement site and the diffusion of urea away from the placement site were responsible for the poor performance of granular urea phosphate in highly calcareous soil. It is concluded that urea‐urea phosphate mixtures should probably not be recommended as a means of reducing ammonia volatilization on highly calcareous soils, though its use on noncalcareous soils and soils low in CaCO3 merits further testing.
Development and Validation of a Numerical Model Simulating Evaporation from Short Cores
Authors: Reynolds W. D. , Walker G. K. 
Published: July 2010

AbstractA theoretically‐based assessment of the short core evaporimeter technique for measuring evaporation from the soil surface can be conducted using numerical simulation. As an initial step, a numerical model is developed that simulates evaporation from isothermal, homogeneous, finite soil columns with a specified initial water content profile. Features of this model include nonlinearized solution of the highly nonlinear surface boundary condition, automatic adjustment of time‐step size according to a mass balance criterion, remaximization of program efficiency at each time‐step, and the use of soil surface temperature as the primary forcing function. The validity of the model was established through its ability to realistically simulate the constant and falling rate stages of soil drying, including root‐time behavior, and by its good mass conservation and stability characteristics. Drying of a clay soil with an initial uniform water content of 0.40 cm3w cm‐3pm for 12 000 min under a constant evaporative demand of 4.4 × 10−4 cm3w cm‐2pm min−1 could be simulated with a time‐step size ranging from 10 to 13.7 min, a specific mass (i.e. flux) balance of < 3%, a cumulative mass balance of < 0.3%, and with generally < five iterations per time‐step. A discretization analysis revealed that for the first centimeter below the soil surface a 0.2‐cm nodal spacing was required to obtain accurate estimates of the evaporative flux and the near‐surface water content profile. Below that depth, however, nodal spacing can be greatly increased without serious reduction of accuracy. Successful validation of the model supports extension to field conditions.
Engineering Properties of Soils as Related to Mineralogy and Particle‐Size Distribution
Authors: Harris W. G. , Zelazny L. W. , Parker J. C. , Baker J. C. , Weber R. S. , Elder J. H. 
Published: July 2010

AbstractRelationships between engineering properties and mineralogical and particle‐size variables were determined for samples from B and C horizons of selected soils. Measurements were made of internal friction (φ), California bearing ratio (CBR), and compression index (Cc). Particle size was determined by pipette analysis and mineral weight fractions were estimated on a clay, silt, sand, and whole‐soil basis using X‐ray diffraction and fluorescence, differential scanning calorimetry, and petrographic grain count analyses. Values of φ and CBR decreased with increasing whole soil phyllosilicate content (kg/kg) and decreasing particle size. Compressibility increased with increasing whole soil phyllosilicate content and decreasing particle size. Correlation coefficients between engineering parameters and most mineral weight fractions for isolated size fractions were low, but interactions between mineralogical and particle size variables were significant. Multiple linear regression models relating φ, CBR, and Cc to soil variables were highly significant, and R2 values for models were high. Interactions of transformed particle size and mineralogical variables were strong contributors in φ and CBR models. Signs of regression coefficients were consistent with the hypothesis that strength decreases and compressibility increases with decreasing particle size and increasing phyllosilicate content.
Comparison of Models for Determining Stability Constants of Metal Complexes with Humic Substances
Authors: Fitch Alanah , Stevenson F. J. 
Published: July 2010

AbstractSeveral recent approaches for determining apparent stability constants of metal complexes with humic and fulvic acids are shown to represent graphical modifications of the basic equation relating the formation function of binding (v = sites bound/macromolecule concentration) to stability constants for the system v = ΣnjKj(M)/Σ[1 + Kj (M)], where Kj is the stability constant for binding at class j, nj is the number of binding sites of class j, and (M) is the free metal ion concentration. They include the Scatchard [v/(M) vs. v], reciprocal [1/v vs. (M)], and double reciprocal [1/v vs. 1/(M)] plots. Another approach is shown to have the same form as the Hill plot, which is based on an assumption of positive cooperativity. Comparison of the various models using a common set of experimental data revealed that approaches based on an assumption of linearity yield poor estimates for stability constants. Of the various models, the Hill plot is the least reliable.