bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tall Fescue Response to Placement of Urea/Ammonium Nitrate Solution
Authors: Moyer J. L. , Sweeney D. W. 
Published: July 2010

AbstractSeveral studies have shown that cool‐season grasses may respond more to subsurface (knife) applications of fluid fertilizer than to surface applications. However, optimum depth of knife application has not been clearly identified. A field study was conducted from 1984 to 1986 to determine the effects of 5‐, 10‐, and 15‐cm knife and surface band (dribble) and broadcast applications of urea/NH4NO3 solution at 84 and 168 kg N ha−1 on forage yield and N use of tall fescue (Festuca arundinacea Schreb.), and on soil N levels. The soil is a Parsons silt loam (fine, mixed, thermic Mollic Albaqualf). In 1985 and 1986, 168 kg N ha−1 resulted in higher final forage yields than 84 kg N ha−1. Knife applications at 10 cm generally resulted in the highest forage yield, though not always significantly higher than other placements. Knife placement at 15 cm resulted in lower N uptake in early grass clippings (intermediate harvests), compared with surface and shallower knife applications. The N concentration, N uptake in the final spring harvest, and apparent fertilizer‐N recovery by the forage were usually increased by 10‐cm placement. Knife applications of N at or below 10 cm resulted in higher inorganic soil N concentrations at intermediate harvests than did surface applications.
Analyses of Adsorption Kinetics Using a Stirred‐Flow Chamber: I. Theory and Critical Tests
Authors: Bar‐Tal Asher , Feigenbaum Sala , Sparks Donald L. , Pesek John D. 
Published: July 2010

AbstractThe study of ion‐exchange kinetics on soils and soil constituents has attracted much interest throughout the last decade. The introduction of a stirred‐flow method to study these reactions, as well as other adsorption‐desorption phenomena, has stimulated this interest. However, the manner in which rate data are interpreted using this technique and other flow methods has been questioned. Accordingly, a numerical solution for various instantaneous equilibrium and kinetic models is presented. It was found that rate data that could be described using an instantaneous equilibrium model could also be interpreted using a kinetic model. Therefore, the validity of kinetic rate coefficients obtained by flow methods is questionable. An analytical approach was developed to outline experimental methods that could be used to distinguish between instantaneous equilibrium and time‐dependent reactions and to differentiate between solution‐concentration‐dependent kinetic models vs. those that are independent of solution concentration. By using this approach, and employing various flow rates and influent concentrations, as well as using a stopped‐flow technique, it is easy to decide whether rates of reactions can be measured using the stirred‐flow method for specific experimental conditions.
Ion Chromatographic Determination of Total Metals in Soils
Authors: Basta N. T. , Tabatabai M. A. 
Published: July 2010

AbstractAn accurate and precise ion chromatographic (IC) method for determination of total Cu, Ni, and Zn in soils was developed. The sample preparation method consists of three steps: (i) digestion of the soil sample by using HNO3, HClO4, and HF; (ii) extraction of the metals of interest by using dithizone in CHCl3; and (iii) destruction of the metal‐dithizonate complex with HNO3. The system consisted of a guard (HPIC‐CG5) column and a separator (HPIC‐CS5) column followed by postcolumn reaction with 4‐(2‐pyridylazo) resorcinol (par), to form colored metal complexes. The absorbance of the metal‐par complexes was measured by an ultraviolet‐visible light (uv‐vis) detector at 520 nm. Two different eluents were required for separation of these and other metals. Simultaneous determination of Cd, Cu, Mn, and Zn was achieved by using an eluent containing 4 mM 2,6‐pyridinedicarboxylic acid (pdca) and 50 mM HOAc‐NaOAc buffer (pH 4.8). Simultaneous determination of Cu, Ni, Pb, and Zn was accomplished by using an eluent containing 40 mM oxalic acid and 50 mM HOAc‐LiOAc buffer (pH 4.8). Results by the IC method for determination of total Cu, Ni, and Zn in 14 soils were in good agreement with those obtained by atomic absorption spectrophotometry, but results also showed that the proposed IC method is inadequate for determination of total Cd, Mn, and Pb in soils.
Humic Substances Formed during the Composting of Organic Matter
Authors: Inbar Y. , Chen Y. , Hadar Y. 
Published: July 2010

AbstractHumic substances (HS) were extracted from separated cattle‐manure compost (CSM) at various stages of decomposition. Carbon‐13 nuclear magnetic resonance (13C‐NMR) and Fourier‐transform infrared (FTIR) spectroscopy measurements were performed on the purified humic acids (HA) as well as crude fiber and chemical analyses. Levels of HS extracted from the CSM samples doubled during the composting (from 377 to 710 g kg−1 organic matter [OM]). The HS were divided into: (i) HA, which increased from 184 to 457 g kg−1 OM; and (ii) a fulvic fraction (FF). The FF was separated on XAD‐8 resin to: (i) fulvic acid (FA), which maintained an unchanged level during composting (80–100 g kg−1); and (ii) a nonhumic fraction (NHF), which increased from 107 to 170 g kg−1 OM during the process. The ratios between the concentrations of these fractions were tested as humification indexes. These indexes changed significantly during the process and were found to correlate exponentially with the composting time, C/N ratio, or both. Quantities of low‐molecular‐weight components (FF and NHF) rapidly increased during the first 40 d of composting and were nearly constant thereafter. The HA and HS contents reached nearly constant values after ∼90 d. Only slight compositional and structural changes in CSM HA were detected with cross‐polarization magic‐angle spinning (CPMAS) 13C‐NMR, FTIR spectra, and chemical analyses. The elemental composition and functional groups of CSM HA resembled those reported for HA of plant residues, peats, and incompletely humified materials. The CPMAS 13C‐NMR spectra of the CSM HA resembled that of lignin. The aromaticity of the HA was about 40% and the lignin content was approximately 60%. The NMR data correlated well with results obtained by FTIR spectroscopy, both indicating that the CSM HA are composed of partially degraded constituents of plant tissue, which still retain to some extent their chemical structures. The major plant components identified in the HA were lignin, carbohydrates, and long‐chain aliphatic structural groups.
Kinetics of Carbon Dioxide Evolution in Relation to Microbial Biomass and Temperature
Authors: Blet‐Charaudeau Catherine , Muller J. , Laudelout H. 
Published: July 2010

AbstractIntensification of agricultural practices on calcareous soils leads to drastic changes in biogeochemical processes due to modifications of CO2 partial pressure in soil pores. For this reason, CO2 evolution was measured in vitro from Typic Rendoll soils of the Champagne Crayeuse at four temperatures. Microbial biomass was also estimated by a plate‐count technique that had been calibrated by two independent methods: chloroform fumigation and bioluminescence. Carbon dioxide evolution curves fit an equation consisting of a zero‐ and first‐order reaction. The three parameters of this equation were interpreted as: (i) the amount of easily decomposable organic matter generated by the disturbance, (ii) the time constant for the disappearance of that disturbance, and (iii) the sustained respiration of the native microflora. This model implies that the rate of CO2 evolution is maximum at the start of the incubation, while the observed maximum in bacterial biomass occurred about 5 d later. Comparison of the results presented here with data from the literature shows that there is an almost continuous spectrum of values for the amounts of easily decomposable organic matter generated by any disturbance, and that the time constant for its mineralization is of the order of a very few days. Therefore, the use of the double exponential model is superfluous unless the duration of the incubation experiments exceeds 100 d.
Soil‐Geomorphic Relations on the Blue Ridge Front: I. Regolith Types and Slope Processes
Authors: Graham R. C. , Daniels R. B. , Buol S. W. 
Published: July 2010

AbstractRegolith distributions and characteristics were related to slope processes along two transects in mica gneiss and mica schist terrane on the Blue Ridge Front of North Carolina. Regolith types are saprolite, soil residuum, and colluvium. Saprolite is thickest on low slope positions, where throughflow moisture promotes weathering and overlying colluvium protects the saprolite from mass wasting. Saprolite is thinnest on shoulders and backslopes, where mass wasting and rapid runoff inhibit its formation. Rock outcrop is most common on backslopes. Soil residuum, present on most landscape positions, comprises the entire regolith above saprolite only on the broad, nearly level ridge top. The pedogenic transformation of saprolite to soil residuum resulted in higher clay contents and redder hues through in situ weathering and illuvial accumulations. On sloping terrain, saprolite or soil residuum is overlain by colluvium. Lower slopes contain thick deposits of landslide colluvium. Colluvium from slope wash and soil creep comprise the upper 10 to 20 cm of regolith on all sloping surfaces. Colluvial deposits, excluding A and E horizons, are uniform in color, the result of homogenization during transport. Mass movement has also served to physically break down chemically weathered mica grains, releasing secondary minerals into finer size fractions. Knowledge of slope processes assists interpretation of regolith weathering history, which is important for understanding soil parent materials.
Aggregate Stability in the Palouse Region of Washington: Effect of Landscape Position
Authors: Pierson F. B. , Mulla D. J. 
Published: July 2010

AbstractAn extensive study was conducted to measure spatial patterns in aggregate stability in the steep, hilly, and highly erodible loessial soils of the Palouse region in southeastern Washington. Soil samples were collected at 20‐m spacings along four 800‐m‐long transects within a winter wheat field and analyzed for aggregate stability at a slow and a fast rate of wetting, organic C, amorphous Fe, soil water content, and particle size distribution. Aggregate stability under slow wetting, organic C, and clay content were significantly different at summit, shoulder, toeslope, and footslope positions on the landscape. More specifically, aggregate stability and organic C content were highest in footslope and toeslope positions, and lowest at the summit. Clay content was highest at the summit and lowest in footslope positions. Aggregate stability at a fast rate of wetting had a coefficient of variation (40%) that was nearly double that for slow wetting, and was not well correlated to either landscape position or measured soil properties. The variation in aggregate stability under slow wetting could be modeled in terms of organic C content and elevation. Other properties such as amorphous Fe and water or clay content were only weakly correlated to aggregate stability. Thus, although the spatial patterns in aggregate stability exhibited moderate variability (CV = 22%), the patterns were closely related to changes in a few key properties, namely, organic C content and landscape position. A likely explanation for these findings is that soil erosion removes the topsoil and organic matter from the ridgetops, thus exposing subsoil horizons, which are higher in clay content and lower in aggregate stability.
Modeling Potassium Uptake by Slash Pine Seedlings from Low‐Potassium‐Supplying Soils
Authors: Van Rees K. C. J. , Comerford N. B. , McFee W. W. 
Published: July 2010

AbstractThe application of diffusion/mass‐flow theory to K uptake by slash pine (Pinus elliottii Engelm. var. elliottii) seedlings from low‐K‐supplying soils is presented. Simulations for K uptake were evaluated by the Barber‐Cushman model (BCM) and the Baldwin‐Nye‐Tinker model (BNTM) under greenhouse and field conditions. Potassium uptake was overpredicted by 31 to 50% in greenhouse studies; overestimates, however, are attributed to nonuniform distribution of roots along pot walls. Simulations underpredicted K uptake by 0.48 and 0.83 times that observed in seedlings grown in the field. Although ectomycorrhizal hyphae were abundant in the field, their contribution to K uptake was not incorporated. Predictions of K uptake were excellent for seedlings grown at a tree nursery when fertilizer amendments were included. The BNTM, based on simplifying assumptions, predicted K‐uptake values similar to the BCM. Sensitivity analysis showed that root growth and initial K concentration in soil solution were the two most important factors affecting K uptake by slash pine. Soil processes that control K concentration were the limiting factors to K uptake on these soils. Monte Carlo procedures indicated that, for two harvests in the field, simulated estimates of uptake had CVs ranging from 34 to 64%.
Nutrient Cycling in a Red Pine Plantation Thirty‐Nine Years after Potassium Fertilization
Authors: Shepard James P. , Mitchell Myron J. 
Published: July 2010

AbstractRed pine (Pinus resinosa Ait.) plantations planted in the late 1920s and early 1930s at the Pack Forest near Warrensburg, NY, showed severe nutrient deficiency symptoms after a few years. Numerous investigations revealed the soil to be extremely K deficient, due to a century of agricultural use. The present study was undertaken to describe long‐term effects of K fertilization and to more completely characterize nutrient cycling in K‐fertilized plantations and thus describe mechanisms responsible for the longevity of the K‐fertilization response. In 1948, three 0.04‐ha plots were established; two were fertilized with either 59 or 118 kg ha−1 K (designated LO and HI, respectively) and the third left untreated (CTL). Fertilization increased radial increment for ∼10 yr and resulted in increased basal area and tree height. In 1987 (39 yr after fertilization), soil exchangeable K in the upper 15 cm of the mineral soil remained greater in fertilized plots. Aboveground biomass in 1987 was 129, 164, and 190 Mg ha−1, respectively in CTL, LO, and HI. In LO and HI, the N, P, Ca, Mg, and Na contents were 20 to 50% greater than in CTL. There was twice as much K in the aboveground vegetation of LO and HI than CTL, due primarily to increased foliar biomass. This was reflected in the greater litterfall as well as throughfall and stemflow fluxes of K in LO and HI relative to CTL. Fertility of the plots was maintained by the efficient cycling of nutrients, especially K, in the ecosystem.
Ammonia Volatilization from Flooded Soil Systems: A Computer Model. III. Validation of the Model
Authors: Jayaweera G. R. , Paw U. K. T. , Mikkelsen D. S. 
Published: July 2010

AbstractAn NH3‐volatilization model predicting NH3 loss as a function of five input variables was validated using a wind tunnel to simulate rice paddy conditions and direct field experiments. A total of five variables in a central composite statistical design were compared to study the interactive effects of NH4‐N concentration, pH, temperature, wind speed, and water depth. Experiments were also conducted in a flooded rice field with polypropylene basins placed at water level. Samples were collected every hour for determination of NH4‐N concentration. Temperature, pH, and wind speed were recorded continuously, and water depth was constant. Wind‐tunnel data showed that the model predicted observed values with excellent accuracy in the range of conditions found in flooded rice systems. The regression of predicted NH3 loss on observed losses resulted in an r2 of 0.98 and a regression slope of 0.99. Field experiments also showed very close agreement between predicted and experimental values with 6‐, 12‐, and 24‐h averages of pH, temperature, and wind speed. The model validation confirmed the theory that NH3 volatilization is a function of NH3(aq) concentration and the volatilization rate constant for NH3, which are dependent on five variables: floodwater NH4 concentration, pH, temperature, water depth, and wind speed. The model is theoretically sound and predicts NH3 loss with a high level of accuracy using a menu‐driven computer program with easily measurable variables, and can be used in comparison studies of NH3 loss at the same site.
Effect of Soil Properties on Unsaturated Hydraulic Conductivity Pore‐Interaction Factors
Authors: Schuh W. M. , Cline R. L. 
Published: July 2010

AbstractThe variability of the pore‐interaction factor, ρ, for a microscopic model proposed for predicting unsaturated hydraulic conductivity, K(θ), from soil water‐retention, Ψ(θ), data was examined in relation to soil particle‐size data and indices, bulk density, organic C, parameters for the van Genuchten Ψ(θ) function, an index (W) of total energy of drainage and soil‐series, toposequential, and geographic groupings. The ρ exhibited no trend relationship to any of the soil properties tested. However, a change in the distribution of ρ was observed in relation to the geometric‐mean particle diameter (Gd) and other soil textural variables. For Gd < 0.08 mm, variability was much larger than for soils with Gd ≥ 0.08 mm. The latter consisted entirely of soils in the sand and loamy sand textural groups. A similar distributional relationship also occurred for ρ vs. W. Examination of ρ on three sites of the Hecla soil series and on related toposequential soils indicated that classification of ρ on the basis of soil series or of soil‐association groupings is a feasible strategy for ρ parameter estimation on some soils. The exponential factor η for a macroscopic model was also investigated. The η was found to be related to W as an exponential function over the full data range. However, η vs. W was nearly identical to a linear function for W data extending from 0 to 400 cm‐γ (where γ is the density of water). The η was also strongly related to Gd as a power function, and to other textural variables as exponential functions. The increasing slope of the power function for Gd < 0.08 mm indicated a large potential error of prediction for K(θ) on fine‐textured soils.
Simulating Water Movement in Layered and Gradational Soils Using the Kirchhoff Transform
Authors: Ross Peter J. , Bristow Keith L. 
Published: July 2010

AbstractChanges in soil hydraulic properties with depth are common in field soils and need to be accounted for in simulations of field soil‐water balances. We show that this is possible using the Kirchhoff transform (K transform) when solving Richards' equation numerically, even though the K transform is not continuous across boundaries between layers with different hydraulic properties. The solution is achieved by dividing the soil into depth elements, using the K transform to compute flow within each element, and then using matric potential (which is continuous across boundaries) to couple the elements. Combination of the K transform with iterative, implicit, mass‐conserving methods of solving the flow equations results in efficient solutions that take no more than a few seconds on a personal computer to simulate infiltration. This is achieved with errors of only a few percent in the amount and distribution of soil water. Illustrative simulations using hydraulic properties that represent different soil profiles are given. These include simulation of infiltration into a layered profile consisting of tilled soil with a crust overlying an undisturbed soil, and gradational profiles with hydraulic properties of a sand varying linearly with depth to those of a clay, and conversely. Development and dissipation of surface ponding and perched water tables during simulation runs presented no difficulties. Nor did use of the Campbell formulations for the soil hydraulic properties, despite the discontinuity at the wet end.
Initial Storm Effects on Macropore Transport of Surface‐Applied Chemicals in No‐Till Soil
Authors: Shipitalo M. J. , Edwards W. M. , Owens L. B. , Dick W. A. 
Published: July 2010

AbstractPrevious research has established that macropores can rapidly transmit water through soil. This observation has raised concern that macropores may also promote rapid movement of agricultural chemicals to groundwater. This is a particular concern for no‐till fields where lack of disruption by tillage can lead to the development of extensive macropore systems. In order to investigate the effect of initial rainfall on chemical transport, strontium bromide hexahydrate (SrBr2·6H2O) and atrazine (2‐chloro‐4‐ethylamino‐6‐isopro‐pylamino ‐s‐triazine) were surface‐applied to six 30 by 30 by 30 cm blocks of undisturbed soil obtained from a 25‐yr‐old, no‐till corn (Zea mays L.) field with evidence of well‐defined macropores attributable to earthworm activity. Half of the blocks then received a 1‐h 5‐mm simulated rain, which did not produce percolate. Two days later, the blocks received a 0.5‐h 30‐mm simulated rain, followed by another 0.5‐h 30‐mm rain 1 wk later. The remaining blocks received only the two 30‐mm events. An average of 12% of the applied water passed through all the blocks during and shortly after the first 30‐mm rain. Bromide, Sr, and atrazine losses in this percolate were 7, 10, and 2 times less, respectively, from blocks that received the 5‐mm rain than from blocks not receiving this initial, light rain. The second 30‐mm rain on the blocks not receiving the initial 5 mm produced 1.6× more percolate than the first 30‐mm rain. Yet, transport and flow‐weighted average concentrations of Br, Sr, and atrazine were all reduced. These results indicated that the first storm after application can move solutes into the soil matrix, thereby reducing the potential for transport in macropores during subsequent rainfall events.
Further Comparison of Spatial Methods for Predicting Soil pH
Authors: Laslett G. M. , McBratney A. B. 
Published: July 2010

AbstractSpatial prediction methods have been compared using a carefully and specially designed survey of soil pH. Outliers seriously affected the performance of all prediction methods, and were removed for the comparison. Interpolators, Laplacian smoothing splines, and intrinsic random functions all behaved problematically, and universal kriging using parameter estimates obtained by the novel method called restricted maximum likelihood (reml) was consistently best. The data set contained an apparently obvious trend, but prediction by universal kriging was not improved by including this trend. The inclusion of close pairs stabilized the prediction methods, but there was no dramatic improvement with reml universal kriging, the best method for this data set.