bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extraction Procedure for Determining Solution and Exchangeable Ions on the Same Soil Sample
Authors: Phillips I. R. , Bond W. J. 
Published: July 2010

AbstractA procedure is described which allows the ionic composition of the soil solution and exchange phases to be measured on the same small soil sample. This procedure is based on existing methods which use a dense, water‐immiscible liquid to displace soil solution during high speed centrifugation. Exchangeable ions are then extracted by shaking the soil with 1.0 mol L−1 ammonium acetate (pH 7), after which the soil is oven‐dried and the water content determined. The solution extracted from the soil sample accurately represents the ionic composition of the equilibrium soil solution and the procedure does not affect the ionic composition of the exchange phase.
Dispersion of Three Andic Soils by Ultrasonic Vibration
Authors: Hunter Craig R. , Busacca Alan J. 
Published: July 2010

AbstractA probe‐type ultrasonic vibrator was used to disperse, without chemical pretreatments, samples of three soils developed from volcanic ash. The efficiency of dispersion by ultrasonic vibration was evaluated using curves of percent clay or sand vs. vibration time along with electron micrographs of sand (50–2000 µm), coarse silt (20–50 µm), and clay (<2 µm) size fractions. Ultrasonic vibration for 900 s at an energy of 39.9 W/cm2 was sufficient to disaggregate the soils without significantly damaging primary sand‐ and silt‐sized glass shards or destroying imogolite threads in the clay fraction.
Water Transport in Unsaturated Nonisothermal Salty Soil: I. Experimental Results
Authors: Nassar I. N. , Horton Robert 
Published: July 2010

AbstractThis paper presents observed soil moisture redistribution within unsaturated soil in response to imposed boundary temperatures. Both salinized and solute‐free soil conditions are studied. Two different uniform initial soil water contents and solute concentrations are used for the salinized soil columns. Likewise, two different uniform initial soil water contents are used for solute‐free soil columns. High and low boundary temperatures are similar for all of the soil columns. Thus, the experiments are designed to directly observe the impacts of thermal, soil matric, and osmotic gradients on redistribution of soil water. In all cases, appreciable amounts of water move in the direction of decreasing temperature within the soil columns. This is not a general rule of soil water movement, but a result of the uniform initial water content, the presence of solute, and the imposed boundary temperatures under salinized soil, or the initial water content and the imposed boundary temperatures under solute‐free soil. For both solute‐free and salinized soils, the net amount of transported water to achieve steady‐state conditions is greater for low initial water content than for high initial water content. Therefore, the steady‐state variations in the soil moisture content increased by decreasing the initial moisture content. When the same initial water content is used for both salinized and solute‐free soils, the net water transported to achieve steady‐state conditions is greater for the solute‐free soil than for salinized soil. These observations indicate clearly that solute concentration affects soil water transport with unsaturated, nonisothermal conditions.
On the Estimation of Cation Exchange Parameters from Column Displacement Experiments
Authors: Kool J. B. , Parker J. C. , Zelazny L. W. 
Published: July 2010

AbstractA procedure is presented for estimating cation exchange capacity (CEC) and exchange selectivity coefficients from miscible displacement experiments on undisturbed soil columns. The procedure provides an alternative to batch experiments and is applicable to scenarios involving either binary homovalent exchange or binary monodivalent exchange. Gapon's exchange equation is used in the latter case. Parameters are determined by nonlinear, least‐squares inversion of column effluent concentration histories. The procedure requires that hydraulic flux and total solution normality be kept constant. It is also assumed that ion exchange takes place instantaneously. When this assumption is violated, it is still possible to obtain a good description of the observed data, but the parameter estimates may be meaningless. The feasibility of estimating the dispersion coefficient in the advection‐dispersion equation along with the ion exchange parameters is evaluated. Results indicate that this is generally not possible for continuous injection experiments, but much better results are obtained for pulse injection experiments.
A Compact Constant‐Head Permeameter for Measuring Saturated Hydraulic Conductivity of the Vadose Zone
Authors: Amoozegar A. 
Published: July 2010

AbstractMost procedures for determination of saturated hydraulic conductivity (Ks) of the vadose zone are difficult to perform and time consuming. Recent developments have shown that Ks can be determined by the constant‐head well permeameter technique with a few liters of water in less than 30 min using small‐diameter auger holes. A compact constant‐head (CCH) permeameter is designed for maintaining a constant height of water (>5 cm) at the bottom of a 4‐ to 10‐cm‐diam. hole in the unsaturated zone, and measuring the amount of water flowing into the hole. The main unit of the CCH permeameter is used for measuring Ks from the soil surface to a depth of 2 m. To determine Ks below 2‐m depth a special flow‐measuring reservoir, equipped with a portable pressure transducer, is connected to the device and inserted to the bottom of the hole. The CCH permeameter has a water‐holding capacity of 5 L, can be used on any landscape position without an external support, and can be easily transported in the field. The device has been tested in the laboratory and field, and is capable of delivering a maximum flow rate of 3 × 10−6 m3 s−1.
Determining Soil Salinity from Soil and Soil‐Paste Electrical Conductivities: Sensitivity Analysis of Models
Authors: Rhoades J. D. , Waggoner B. L. , Shouse P. J. , Alves W. J. 
Published: July 2010

AbstractModels and relations used to determine soil salinity (ECe) in the field from measurements of bulk soil electrical conductivity (ECa), or from saturated soil‐paste electrical conductivity (ECp), and estimates of other influential soil parameters were analyzed to evaluate the degree to which salinity appraisal is affected by inaccuracies made in the estimates. Results show that the values of the parameters which can not be easily measured in the field (i.e., bulk density (ρb), particle density (ρs), clay percentage (% clay), and total and “immobile” volumetric soil water contents (θw and θws, respectively) can be estimated sufficiently accurately for the purposes of practical soil salinity appraisal.
Mechanisms of Dissolved Organic Carbon Adsorption on Soil
Authors: Jardine P. M. , McCarthy J. F. , Weber N. L. 
Published: July 2010

AbstractThe subsurface transport of inorganic and organic contaminants may be strongly related to the movement of dissolved organic carbon (DOC) through a soil profile. A variety of soil chemical and hydrologic factors control the mobility of the DOC, which may enhance or impede the transport of the associated contaminants. In this study, the sources of DOC adsorption on two proposed waste‐site soils are defined, and the chemical mechanisms operative during the adsorption process are specified. Adsorption isotherms for the two soils determined at constant pH, ionic strength (I), and temperature indicated that DOC adsorption increased with increasing soil profile depth. Different adsorption capacities were exhibited by the two soils, however, which was related to their contrasting indigenous organic matter contents and mineralogies. The adsorption of DOC by the soils was not a function of solution I (I = 0.001 to 0.1 mol L−1 using NaCl); however, DOC adsorption was dependent on solution pH, with maximum adsorption occurring at ≃4.5. Competitive ion‐exchange studies using Na2SO4 as an ionic‐strength adjuster suggested that a portion of the DOC was electrostatically bound to the soil via anion exchange. By using thermodynamic principles, the predominant mechanism of DOC retention by the soil was found to be physical adsorption driven by favorable entropy changes. This is supported by preferential adsorption of the hydrophobic organic solutes to the soil relative to the hydrophilic organic solutes.
Direct Determination of Aluminum and its Cationic Fluoro‐Complexes by Ion Chromatography
Authors: Willett I. R. 
Published: July 2010

AbstractAn ion chromatographic method was developed for the direct determination of monomeric Al (Al3+, and hydroxo‐, sulfato‐, oxalato‐, and fluoro‐ complexes). Separations were made in one run in 4 min with a 50 mm low‐capacity cation exchange column, and detected by postcolumn reaction with pyrocatechol violet. Three peaks corresponding with mono‐, di‐ and trivalent species were obtained. The last peak also included the hydroxo‐Al and sulfato‐Al species. The AlF2+ species could be determined directly, but AlF+2 coeluted with the monovalent oxalato‐ species. Citrato‐Al species were not detected because of the inability of pyrocatechol to decouple the complex in the time frame of the analysis. Concentrations of Al down to 2 µM could be determined with 200 µL injections. The results for 21 Al‐F solutions closely matched those predicted from a chemical equilibrium program. The method was applied to extracts of 10 soils and it was found that Al3+, including hydroxo‐Al species, and AlF2+ were dominant. Limitations to the application of the method to soils included coelution of AlF+2 with monovalent organic species that are able to be decoupled by pyrocatechol, and blockage of the column end frits by solutions containing more than 200 mg L−1 of humic acid. The ion chromatographic method is the first to directly determine AlF2+ and other well‐defined forms of monomeric Al. It is rapid and can be fully automated.
Residual Effects of Nitrogen Fertilization and Winter Cover Cropping on Nitrogen Availability
Authors: McCracken Daniel V. , Corak Steven J. , Smith M. Scott , Frye Wilbur W. , Blevins Robert L. 
Published: July 2010

AbstractLong‐term management practices affect the reserve of mineralizable soil N, and so can influence the amount of supplemental N fertilizer required in crop production. This study was conducted to (i) evaluate the residual effects of long‐term N fertilization and winter cover cropping on corn (Zea mays L.) N nutrition, and (ii) examine the ability of selected soil indices to detect management‐induced differences in soil N availability. In 1986, N fertilizer and winter cover crops were eliminated from plots which, from 1976 through 1985, had received varying tillage treatments, N fertilizer additions, and either hairy vetch (Vicia villosa Roth), rye (Secale cereale L.), or no winter cover crop. A history of N fertilization increased corn yield and N uptake (by an average of 20.4 kg N/ha). A history of winter cover cropping with hairy vetch increased corn yield and N uptake (by an average of 28.0 kg N/ha). Rye cover cropping generally had small or inconsistent effects relative to no cover crop. Tillage generally had insignificant effects on corn yield and N uptake. Soil N availability indices were determined on surface samples (0–15 cm) taken 2 wk after corn planting. The anaerobic incubation provided a poor index of N availability. Total soil C and Kjeldahl N were affected by tillage, though not by cover crop or fertilization history, and were marginally correlated with crop response. The autoclave index was only slightly superior to total soil C and Kjeldahl N as a N‐availability index. The soil NO3‐N concentration was highly correlated with corn yield, and N uptake. Though this study was conducted for 1 yr at one site, results indicate that measurement of surface soil NO3‐N made shortly after corn planting can provide a valid index of the effects of past crop and soil management practices on soil N availability to corn.
Variability of the Cecil Map Unit in Appomattox County, Virginia
Authors: Thomas P. J. , Baker J. C. , Simpson T. W. 
Published: July 2010

AbstractA study was initiated in Appomattox County in the southern Piedmont of Virginia to assess composition and variability of a Typic Kanhapludult map unit. Five delineations of the Cecil (clayey, kaolinitic, thermic Typic Kanhapludults) map unit, three to eight sites within each delineation, and three profiles within each site were randomly located in a two‐level nested sampling scheme. Soil physical, chemical, and morphological data were collected from the Ap, Bt, and BC horizons of each profile. Fifty‐eight percent of the 81 profiles met the criteria for the Cecil soil series. Seventy‐one percent of the profiles were taxonomically similar to Cecil. The remaining 29% were taxonomically dissimilar inclusions. Thus, the map unit name would be Cecil and the map unit description would include dissimilar soils. Taxonomic variability was reflected in variability of taxonomically important soil properties. Percent base saturation decreased with depth in the profile. Maximum clay distribution occurred in the Bt horizon and ranged from 25 to 75%. The solum exhibited large variation in thickness. Subsoil properties important to mapping (percent base saturation in the chemical control section, clay percentage in the particle‐size control section, and solum thickness) exhibited considerable variation within delineations but the variability was consistent from delineation to delineation. Intrusions of mafic material into the felsic crystalline system, from which Cecil and similar soils form, accounted for most of the variability in the soil properties.
Long‐Term Effects of No‐Tillage, Crop Residue, and Nitrogen Application on Properties of a Vertisol
Authors: Dalal R. C. 
Published: July 2010

AbstractThere is a paucity of information on the long‐term effects of crop residue management under no‐tillage culture on properties of clay soils in tropical and subtropical regions. The objective of this study was to compare the effects of 13 yr of conventional tillage vs. notillage, crop residue retained vs. burned, and no fertilizer N vs. application of 23 and 69 kg N ha−1 yr−1 on organic C content, total N, mineralizable N, pH, electrical conductivity, chloride, exchangeable sodium percentage (ESP), and aggregation index (undispersed fraction <20 µm silt + clay) in a fine‐textured Vertisol (650 g clay kg−1 soil). Highest concentrations of organic C and total N were found in the surface soil (0–0.1 m) with a combination of no‐tillage, crop residue retained, and fertilizer N. Mineralizable N followed similar trends. Soil pH to 0.3‐m depth and electrical conductivity to 1.2‐m depth were significantly lower under no‐tillage than under conventional tillage. Aggregation index of the surface soil (0–0.1 m), was higher under no‐tillage. The ESP was lowest in the surface soil (0–0.04 m) under no‐tillage with crop residues retained; the soil profile (0–1.2 m) under this treatment also contained far less NaCl‐equivalent salts (0.8 Mg ha−1) than under conventional tillage with crop residue burned (7.3 Mg ha−1). Available water and nitrate were lower in the surface soil but greater at depths (0.6–1.2 m) under no‐tillage than in tilled soil. Thus tillage and crop residue management can substantially affect soil organic matter and microbial activity in the surface layers, and water relations and salt movement to at least 1.2‐m depth, even in a fine‐textured Vertisol.
Effects of a Conditioner on Soil Physical Properties
Authors: Fitch Bryan C. , Chong S. K. , Arosemena J. , Theseira G. W. 
Published: July 2010

AbstractAgri‐SC, a soil conditioner manufactured by Four Star Agricultural Services, Inc., Bluffton, IN, was applied to a fallow Stoy silt loam (fine‐silty, mixed, mesic Aquic Hapludalf) at rates of 0, 0.15, 0.30, and 0.60 L/ha for two successive years. After application, the following soil parameters were measured: organic matter content, mean aggregate diameter, porosity, 48‐h aeration porosity, sorptivity, saturated hydraulic conductivity, liquid limit, plastic limit, in situ infiltration and drainage rates, and soil water retention (up to 240 cm of suction). None of the soil properties differed significantly among treatments, but all decreased significantly the second year, except liquid limit. The detrimental effects to soil physical, hydrological, and rheological properties could be caused by the decreases in organic matter.
Predicting Douglas Fir Growth and Response to Nitrogen Fertilization in Western Oregon
Authors: Miller R. E. , McNabb D. H. , Hazard J. 
Published: July 2010

AbstractThe accurate prediction of which Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] stands may or may not respond to N fertilization should improve the economics of the practice. Our objective was to determine the efficacy of various stand (site index, age, and relative density), climatic (total precipitation, average daily solar radiation), site (elevation, soil depth, and available water‐holding capacity), and soil‐test variables (anaerobically mineralized N, total N, organic matter, and C/N ratio) to predict relative and absolute response to a single application of 224 kg N ha−1 as urea. The core equation with stand variables accounted for 70% of residual variation in average annual volume growth. Predicting response of fertilized stands proved much less precise. The best core equation explained 37% of the residual variation for average percentage response in volume growth and explained less variation in absolute response in both volume and basal area. Of the site, climatic, and soil‐test variables, C/N ratio in the surface soil was the only one that significantly increased precision of the core equations. The best combined equation explained 46% of the variation in percent volume response. The anaerobic N mineralization test failed to make a significant contribution to the core equation and had a lower correlation with response than did the C/N ratio. Stand variables remain the most reliable predictors of fertilizer response in this region; any improvement from including soil data for N or organic matter is not justified because of their additional cost.
Burley Tobacco Response to Band Applications of N‐P‐K Fertilizer
Authors: Sims J. L. , Wells K. L. , Calvert J. R. , Schwamberger E. C. , Greer E. C. 
Published: July 2010

AbstractImproved fertilizer management systems for hurley tobacco (Nicotiana tabacum L.) are needed to reduce the detrimental effects of large applications of fertilizer, such as fertilizer‐induced soil acidity and Mn toxicity. Field studies were conducted at several locations in Kentucky during 1980 to 1986 to examine the response of tobacco to rates and methods (band vs. broadcast) of application of N‐P‐K fertilizer. Response to banding N‐P‐K fertilizer varied widely among experimental sites and was related to level of NH4OAC‐extractable soil K. At low soil K levels, greater dry matter and cured leaf yields occurred most often for broadcast compared with banded fertilizer. These effects probably resulted from factors affecting the efficient use of K by the plant, including the greater numbers of roots in contact with fertilizer in broadcast treatments. At high soil‐test K levels, greater growth and yield occurred more often from band treatments (as opposed to broadcast). This probably resulted from a reduction in toxic Mn levels and fertilizer salt injury, and from a more favorable balance between K and other nutrients in band treatments. A linear regression revealed that yields from band and broadcast treatments were equal when initial soil‐test K measured 248 kg ha−1. In soils testing high in P and K, the content of plant Mn increased linearly with rate of N‐P‐K fertilizer in broadcast treatments, whereas it was unaffected by fertilizer rate when the fertilizer was banded.
Apparatus for Sampling and Controlling Gas Composition in Redox‐Controlled Soil Slurry
Authors: Guenzi W. D. , Hutchinson G. L. , Beard W. E. 
Published: July 2010

AbstractStudy of the production or consumption in soil of gaseous N compounds at near ambient concentrations requires unique apparatus and procedures. We used a soil slurry that is continuously flushed by a gas stream with controlled composition. Basic components of the system include a reaction chamber equipped to monitor and control slurry pH, Eh, and temperature, flow controllers for precise control of gas flow rates, a mixing chamber for blending inlet gases from different sources, a low‐volume manifold for collecting contamination‐free samples of inlet and exit gases, a dryer to selectively remove water vapor from the exit gases, and a large‐volume sample loop for collecting enough sample gas for NO analysis. The Eh control was accomplished using automated three‐way solenoid valves to select either O2 or an equal flow of inert gas to mix with the gas stream flushing the reaction chamber. Although the gas sampling and gas handling apparatus and procedures described here were designed for an Eh‐controlled soil slurry, we believe they could be easily adapted to other experimental systems that require trace gas sampling and control without contamination from ambient air.
Estimation of Statistical Moments of Spatial Field Averages for Soil Properties and Crop Yields
Authors: Bresler Eshel 
Published: July 2010

AbstractCrop yield variability often results from spatial variability of soil properties. The quantities of practical interest are the spatial averages of these properties over the entire field domain. In this study, correlation scales and the conditional and unconditional first two moments of field averages were estimated, by the maximum likelihood (ML) and Conditional Multi‐Variate Normal methods and numerical approach, for four soil properties, two soil variables, and two crop‐yield components of three field crops. The results show the significant contribution of the conditional approach in reducing the variances of the spatial average yield and soil properties by about an order of magnitude. It is also observed that the estimated conditional expectations of the spatial averages are practically identical to the unconditional one, although the maps of the conditional expectation over the field differ from the maps of the unconditional one. The integral scales of crop yields were found to be roughly estimated from the integral scales of the related soil properties. The use of conditional probability as a practical tool for reducing prediction uncertainty and the potential of conditional analysis to help make practical decisions are demonstrated. The principal practical conclusion is that, although unconditional analysis may be much simpler than the conditional approach, the latter may be more advantageous.
Manganese‐Phosphate Solubility Relationships in an Acid Soil
Authors: Schwab A. P. 
Published: July 2010

AbstractThe chemistry of Mn and P is often complicated by apparent undersaturation with respect to mineral phases. The role of Mn phosphates in controlling the solubility of Mn and PO4 was studied in acid soils which had been fertilized annually for 40 yr with NH4NO3 and superphosphate. Soil pH ranged from 4.1 to 6.8 and available P varied greatly. Fresh, field‐moist soil samples were equilibrated with 0.01 M CaCl2 for 25 d and then analyzed for Mn and PO4 activities. A method was developed to measure redox potential reliably with a Pt electrode to allow calculation of Mn3+ activities. In previous studies, activities of PO4 in these soils were less than the solubilities of strengite (FePO4) and variscite (AlPO4), and Mn activities were less than Mn oxide solubilities. The measured activities of Mn3+ and PO3‐4 were consistent with the presence of MnPO4·1.5H2O but were undersaturated with respect to Mn(II) phosphates.