bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen Fertilization I. Nitrate Accumulation and Losses Under Continuous Corn Cropping
Authors: Hahne H. C. H. , Kroontje Wybe , Lutz J. A.
Published: July 2010

Selected treatments were chosen from three field experiments with corn (Zea mays L.) to determine effects of N rates on the vertical distribution of nitrates in the soil. The experiments were located on three different soil types and corn was grown for 5 consecutive years. Irrigation was a variable in two of the experiments.

Appreciable amounts of NO3‐N accumulated in the soils when the optimum rate of 140 kg N/ha at Blacksburg and Charlotte Courthouse and 168 kg N/ha at Orange had been exceeded. Amounts of vertical distributions of NO3‐N accumulations were highly dependent on soil type, and on amounts of irrigation and rainfall. Lowest NO3‐N accumulations and highest NO3‐N losses were encountered in the Cecil fsl. An increase in NO3‐N was found in the Davidson clay loam whereas no loss or gain was observed in the Groseclose silt loam.

Irrigation markedly reduced the maximum NO3‐N accumulation in the Davidson clay loam especially in the 120 to 195‐cm depth. Irrigation on the Cecil fine sandy loam had less influence on NO3‐N and hardly affected the spread of the accumulation zone. The data indicated that proper irrigation of soils with high internal drainage can markedly reduce NO3‐N loss through leaching; the reduction in NO3‐N loss in the Cecil fine sandy loam was from 48 to 5% at near optimum N rate of application.
Nitrogen Fertilization: II. Effect on the Soil Solution Composition, Acidity, and Nitrate Adsorption
Authors: Lutz J. A. , Kroontje Wybe , Hahne H. C. H.
Published: July 2010

Analyses were performed on soil solution extracts of samples obtained from depths where nitrate accumulation occurred due to ammonium nitrate applications on three different soils, i.e., Cecil fine sandy loam (Typic, Hapludult; clayey, kaolinitic, thermic), Groseclose silt loam (Typic, Hapludult; clayey, mixed, mesic), and Davidson clay loam (Rhodic, Paleudult; clayey, kaolinitic, thermic). Comparisons were made between treatments of moderate and high N applications in all three soils and between irrigated and nonirrigated conditions on the Cecil and Davidson soils.

Nitrate movement and accumulation resulted in markedly different effects on the soil solution composition in the various soils. In the Groseclose silt loam, which has a subsurface layer of low permeability, high nitrate and electrolyte concentrations accompanied by lower pH values and higher amounts of Zn, Mn, and Al in the soil solution were encountered. In the Cecil fine sandy loam and Davidson clay loam, substantial amounts of nitrate were in an adsorbed state which resulted in lower electrolyte concentrations in soil solution. The degree of adsorption was dependent on pH conditions which were affected by movement of acidity. The high NO3‐N adsorbed/NO3‐N solution ratios in the Cecil and Davidson soils indicate that denitrification was not predominant at lower depths in these soils.

The fact that applications of acid‐forming N fertilizers may affect the plant root environment mardedly in some soils and result in increased Mn and Al concentrations in the soil solution also suggest that toxic levels for some plants and crops may occur.
Hydraulic and Thermal Properties of a Sandy Soil as Influenced by Incorporation of Sewage Sludge
Authors: Gupta S. C. , Dowdy R. H. , Larson W. E.
Published: July 2010

Soil‐water retention was increased by incorporation of sewage sludge into a sandy soil. Most of this increase resulted from water adsorbed by organic matter (15‐bar water). At any given water content, unsaturated hydraulic conductivity and soil‐water diffusivity decreased as rates of sludge addition increased. However, saturated hydraulic conductivity increased as rates of sludge addition increased.

Thermal conductivity decreased with increasing rates of sludge application. However, the heat capacity of all oven‐dried sludge‐soil mixtures was the same as that of the control treatment. The combination of a lower thermal conductivity and a higher specific heat (due to higher water content) buffered sludge‐amended soil against sudden temperature changes. Thus, maximum and minimum daily temperatures on plots receiving sludge were a few degrees lower and higher, respectively, than those on the control treatment.
Use of a Versatile Experimental System for Soil Erosion Studies
Authors: Walker P. H. , Hutka J. , Moss A. J. , Kinnell P. I. A.
Published: July 2010

A laboratory facility for the study of soil erosion is described. Rainfall from a modular system supplied raindrops at near terminal velocity to prepared soil beds set in a flume with slope adjustable up to 30%. A comparison was made of erosion under overland flow alone and storm rains of the same intensity (discharge), but different energy levels. Raindrop impact in runoff flow was a powerful agency in promoting soil transport and inhibiting rill formation. Bed‐load movement was important in the transport of sand grains, even where the runoff was disturbed by raindrops.
Solute Transfer, with Exchange between Mobile and Stagnant Water, through Unsaturated Sand
Authors: Gaudet J. P. , Jégat H. , Vachaud G. , Wierenga P. J.
Published: July 2010

Changes in salt concentration with time were measured at several depths inside and at the exit of a 94‐cm uniform unsaturated sand column which was leached at steady rates with solutions of calcium chloride. Observed salt distributions were compared with salt distributions calculated with a numerical procedure which was based on the dead‐end pore model of Coats and Smith (1964).

Values for the dispersion coefficient, the diffusional mass transfer coefficient, and the fraction mobile water used in the model were obtained at different water contents by curve fitting observed and calculated concentrations at one depth. These same values were then used to calculate salt distributions at other depths and at the exit of the column and compared with measured salt distributions. Excellent agreement was obtained. The model presented a good description of the extensive tailing of the salt concentration distributions observed inside and at the exit of the column. The amount of stagnant water was found to increase with decreasing water content from 4% of the total water content of 0.256 cm3/cm3 to 40% of the total water content at a water content of 0.200 cm3/cm3. The apparent dispersion coefficient decreased from 6 cm2/hour to 1 cm2/hour at water contents of 0.256 and 0.200 cm3/cm3, respectively.
Steady Infiltration from a Ditch: Theory and Experiment
Authors: Batu Vedat
Published: July 2010

The two‐dimensional, steady‐state water flow equation, which is based on the assumption that the hydraulic conductivity is an exponential function of the soil water pressure, is solved for a ditch on the soil surface. The results include expressions describing the distributions of matric flux potential and water content. Measured water contents were compared with this mathematical model and also with the models given by Lomen and Warrick (1974) for a line source, and Warrick and Lomen (1976) for a strip source.
Adsorption of Zn by Fe and Al Hydrous Oxides as Influenced by Aging and pH
Authors: Shuman L. M.
Published: July 2010

Zinc solutions were equilibrated with both fresh and aged Fe and Al hydrous oxides to measure Zn adsorption. The data conformed to the Langmuir isotherm, and the Langmuir coefficients for Zn adsorption capacities and bonding energies were determined. The adsorption capacities for the aged Fe oxide (goethite) and the aged Al oxide (gibbsite) were the same. The adsorption capacities for both of the fresh oxides (amorphous) were about 10 times those for the aged oxides which corresponded to a 10‐fold difference between their respective CEC's and surface areas. The bonding energies for Zn for the fresh Al oxide were three times that for the fresh Fe oxide, but the bonding energies for the two aged oxides were the same. Bonding energies were directly related to adsorption capacities. The inflection points on the Zn adsorption vs. pH curves were between pH 5 and 6 for both oxides.
Kinetics of Salt Release from a Saline Soil
Authors: Jurinak J. J. , Whitmore J. C. , Wagenet R. J.
Published: July 2010

The kinetics of salt release from simulated saline sediments was studied to ascertain the potential of sediments as a diffuse source of salinity. Two rate equations were derived, both based on the premise that dissolution was a diffusion controlled process. The equations were ln (1 − C/Cs) = ‐kt and C = k′t1/2, where c is the concentration at any point in the bulk solution, cs is the equilibrium concentration of the soluble soil minerals, t is time, k is the first‐order rate constant, and k′ a proportionality constant. Kinetic data were obtained from a saline typic torriorthent soil derived from Mancos shale in the Price river Basin, Utah. During the initial 72 hours of reaction, dissolution can be described by three, diffusion controlled, reactions. Increasing particle size decreased the rate of reaction. Both derived equations were equally effective in describing salt release.
Efficient and Inefficient Use of Phosphorus by Sorghum
Authors: Brown J. C. , Clark R. B. , Jones W. E.
Published: July 2010

Twelve (Sorghum bicolor L. Moench) genotypes were grown on acid‐Bladen soil (pH 4.3, P stressed or Al toxic), on limed‐Bladen soil (pH 5.2, Cu stressed), and on alkaline Quinlan soil (pH 7.5, Fe stressed) to determine the effect of P efficiency on use of these clements by the plants. Under P‐stress or Al‐toxicity conditions, the most P‐efficient sorghum genotypes absorbed more 32P than the most P‐inefficient lines and grew normally, while the P‐inefficient plants developed P‐deficiency symptoms. Under Fe‐stress conditions, the most P‐efficient genotypes developed Fe chlorosis, while the most P‐inefficient plants remained green. Under Cu‐stress conditions, one of six genotypes developed severe Cu‐deficiency symptoms, characterized by the accumulation of higher P in the lower leaves, and by lower Fe and Ca in upper leaves of Cu‐stressed plants as compared with Cu‐sufficient plants. Thus, P efficiency in plants may be an asset when P availability limits growth, but it may be a liability when these same plants are subjected to Fe or Cu stress.
The Use of COLE Values for Soil Engineering Evaluation
Authors: Hallberg George R.
Published: July 2010

The coefficient of linear extensibility (COLE) measures soil swelling of natural soil clods and was designed for use in soil genesis and characterization studies. In an attempt to quantify engineering ratings of shrink‐swell potential and to enhance nonagricultural use of soil survey data COLE has been statistically related to arbitrary PVC values. However, the data used to calculate COLE can also be used to directly calculate standard engineering parameters: shrinkage limit (SL), shrinkage ratio (SR), and percentage of volumetric change (VC). These values are more widely understood by the potential user as well. COLE is being measured in standard characterization studies by the National Soil Survey Laboratory and forms an immediate data base for quantification of shrinkage factors for soil survey interpretation. SL, SR, and VC can also be calculated from some pedon characterization data measured before the COLE techniques were put into use.
A Light Interception Method for Measuring Row Crop Ground Cover
Authors: Adams J. E. , Arkin G. F.
Published: July 2010

Ground cover determined by light interception is the percentage of the soil surface shaded by the plant canopy; i.e., it is a measure of the shadow projected by the plant canopy. The best time to measure ground cover is near solar noon when changes in solar angle result in the least change in ground cover. Measurements of ground covered by canopy foliage are used to evaluate the effectiveness of sunlight interception in photosynthesis and evapotranspiration studies. Ground cover measurements are also useful indicators of the ability of various row crops and cropping systems to intercept rainfall and reduce runoff and erosion.

Ground cover of grain sorghum [Sorghum bicolor (L.) Moench], cotton [Gossipium hirsutum L.], sunflower [Helianthus annus (L.)], soybean [Glycine max (L.) Merr.], and corn [Zea mays (L.)] were determined using a meter stick, overhead photography, and photosensitive light sensors.

The meter‐stick method is as accurate, faster, simpler, and more economical than any of the other methods used to determine ground cover. There were no significant differences in ground cover determinations using the meter‐stick method, overhead photographs, spatial quantum sensor, or traversing quantum cell. Ground cover was not linearly related to Leaf area index (LAI). A single measurement of ground cover across the plant row (perpendicular) was as accurate as the average of 21 inter‐row measurements parallel to the plant rows.
Oxidation‐reduction Mechanism for Structural Iron in Nontronite
Authors: Stucki J. W. , Roth C. B.
Published: July 2010

Chemical and physical properties of the clay mineral nontronite were studied as the oxidation state of structural iron was altered. Magnesium exchange capacities (CEC) were determined for different nontronite samples that were unaltered, dithionite‐reduced, and reduced‐reoxidized, and were compared to predicted values calculated from the molecular formula. Observed CEC increased from 125 meq/100 g as predicted with increasing Fe2+ content until the Fe2+ content reached about 53 mmoles/100 g then the CEC remained constant at 142 meq/100 g even though the Fe2+ content was increased further to 139 mmoles/100 g. A two‐step mechanism is proposed that involves first, an initial reduction of Fe3+ to a Fe2+ content of 53 mmoles/100 g with an accompanying increase in layer charge and no structural changes; and second, further reduction to a Fe2+ content of 139 mmoles/100 g during which a constant layer charge is maintained by elimination of structural OH and the coordination number of iron in the octahedral sheet is decreased. The mechanism explains changes in oxidation state and electronic environments monitored by Electron Spectroscopy for Chemical Analysis (ESCA) and Mossbauer spectroscopy. The Fe3+(2p3/2) electron binding energy for oxidized nontronite was observed at 711.8 eV, the Mossbauer isomer shift (I.S.) at +0.44 mm/sec and quadrupole splitting (Q.S.) was zero. Hydrazine‐reduced nontronite showed a binding energy at 711.8 eV for Fe3+ and 708.6 eV for Fe2+. Dithionite‐reduced nontronite shifted the binding energy for Fe3+ to 711.0 eV, and Fe2+ remained at 708.6 eV. Mossbauer I.S. moved down to +0.10 mm/sec for Fe3+ and the Q.S. increased to 1.11 mm/sec, and for Fe2+ the I.S. was centered at 1.17 mm/sec with Q.S. near 2.77 mm/sec. The proposed mechanism also accounts for shifts in infrared vibrational energies for the O‐H stretching mode, the FeO‐H deformation, and the Fe‐OH octahedral vibrational modes.
Correcting Turbidity Interference in the Determination of Phosphorus
Authors: Folsom B. L. , Sunderman H. D. , Hossner L. R.
Published: July 2010

Turbidity caused severe interference in the presence of excess ammonium when determining phosphorus by the method of Murphy and Riley. The precipitated complex was isolated and found to be composed of NH4+, antimony, P, and molybdenum in a ratio of 115.8:1.5:1.0:11.6. The combination of Sb and NH4+ in solution during color development caused the turbidity interference. The turbidity could be eliminated by raising the pH above 8.2 with NaOH and boiling to drive off NH4+ as NH3 gas prior to color development or by substituting heat for Sb to develop the characteristic molybdenum blue color.
Tracing the Transformations of Urea Fertilizer during Leaching
Authors: Wagenet R. J. , Biggar J. W. , Nielsen D. R.
Published: July 2010

The transport and transformation of urea, NH4+, and NO3‐ in soil were mathematically described as functions of depth and time, subject to either steady feed or pulse application of N, using relationships derived by assuming diffusion and mass transfer as transport processes and first‐order kinetics as a transformational mechanism. The mathematical model was used to study the enzymatic hydrolysis of urea, nitrification, and denitrification in laboratory soil columns. Urea hydrolysis was found to be independent of initial urea concentration and the O2 concentration of the soil atmosphere. The rate of nitrification under transient N conditions was found to be one order of magnitude greater than the rate of denitrification when there was 20% O2 in the soil atmosphere. Populations of nitrifiers were found to increase in response to successive applications of N.
Erodibility of Selected Clay Subsoils in Relation to Physical and Chemical Properties
Authors: Römkens M. J. M. , Roth C. B. , Nelson D. W.
Published: July 2010

Predictions of soil erodibility factors for selected clay subsoils were studied in relation to physical and chemical properties. Erodibility factors were determined from soil erosion rates on scalped surfaces during a series of simulated rainstorms. Subsoils were analyzed for their textural, chemical, and mineralogical composition. A predictive model, derived from previously gathered data of 46 surface soils, was used to determined the significance of soil properties in predicting subsoil erodibility. Weighted linear regression analysis using data from surface soils of the test model and seven selected subsoils indicated that a textural parameter and the percent of iron plus aluminum extractable with citrate‐dithionite‐bicarbonate (CDB) were significant prediction properties of erodibility for these clay subsoils. Multiple linear regression yielded a prediction equation with a coefficient of multiple determination of R2 = 0.90.
A Laboratory Technique for Appraising in Situ Salinity of Soil
Authors: Mubarak A. , Olsen R. A.
Published: July 2010

A laboratory technique has been devised for removal of solution from soils at field water content. A soil sample can be placed directly in a closable centrifuge tube, thereby minimizing changes which could be induced by altering gaseous equilibria. Water need not be added to the soil sample, so changes in electrical conductivity (EC) and in concentration of species present are avoided. The soil solution is obtained from the sample by immiscible displacement with CCl4 using centrifugation. The technique is simple and relatively rapid. Values for EC in successively displaced solution samples from a given soil sample were found to be essentially constant. The values for EC obtained for an assortment of soils were significantly higher than those obtained using 2:1 or saturation extracts but were well correlated with them.
Salt Effects on the Hydraulic Properties of a Swelling Soil
Authors: Dane J. H. , Klute A.
Published: July 2010

The effects of soil solution composition on the hydraulic conductivity (K) and the volumetric soil solution content (θ) were measured with mixed NaCl‐CaCl2 solutions. The total electrolyte concentration (C) and the sodium adsorption ratio (SAR) characterized the applied solutions. Steady‐state flow cells were constructed with provision for (i) measurement of the volumetric flux of the solution phase during saturated and unsaturated flow conditions, (ii) measurement of the volumetric soil solution content by gamma attenuation, (iii) tensiometers for hydraulic gradient and pressure head (h) measurement, (iv) application of an external load on the soil, and (v) measurement of bulk volume changes. Soil samples were subjected to sequences of solutions varying in C from 1,000 meq/liter to 10 meq/liter at constant SAR values of 0, 5, 15, 25, and 40, respectively. Hydraulic conductivity decreases occurred during the first sequence of decreasing C at fixed SAR values equal to or > 5. The higher the SAR value, the greater the decrease in K with decreasing C. The K decreases occurred at all volumetric soil solution contents within the range of experimental data. Increases in θ, at given h values, and decreases in bulk density (ρb), occurred simultaneously with the decreases in K. Greater changes in K and θ, and smaller changes in ρb occurred in the soil subjected to a higher external load. The K and ρb decreases and the θ increases were to a great extent irreversible, i.e. when C was subsequently increased at a fixed SAR value, K, ρb, and θ did not regain their initial values. Substantial increases in K were obtained, however, if the soil was air dried, sieved, and repacked into the flow cell.
Solute Distribution Profiles Computed with Steady‐State and Transient Water Movement Models
Authors: Wierenga P. J.
Published: July 2010

A comparison is made between two numerical models for simultaneous movement of water and salts in soil profiles. In the first model the water content and flux are constant during irrigation with time or depth (steady state model). In the second model the water contents and fluxes change with time and depth following each infiltration according to the hydraulic properties of the soil (transient model). From a comparison between data obtained with the two models, it is shown that both techniques yield comparable results when concentrations are plotted versus cumulative drainage. Measured effluent concentration distributions from columns periodically irrigated with labeled water, also compare well with effluent concentration distributions computed with the steady‐state model.
Heat Transfer in Dry Aggregated Soil: I. Heat Conduction
Authors: Hadas A.
Published: July 2010

The thermal conductivities of aggregated soils were determined experimentally in the laboratory. As expected the thermal conductivity decreases as the size of the aggregates and the total and interaggregate porosities increase. Good agreement between the measured and predicted thermal conductivity values, by two methods, was found only for small aggregates, but failed increasingly as the aggregate size increased. The discrepencies between measured and predicted values are discussed and are attributed to thermal contact resistance between the soil aggregates that increases as the size and the numbers of the contact points for the aggregates decreases.
Ammonia Volatilization From Soils: Equilibrium Considerations
Authors: Avnimelech Yoram , Laher Malka
Published: July 2010

The volatilization of ammonia from soils as a function of the system's properties is analyzed theoretically and experimentally. The final concentration of ammonium held by the soil increases with an increase in hydrogen ion activity, with the initial ammonium concentration, and with partial pressure of ammonia in the air. An increase in the buffer capacity of the soil leads to a decrease in the final ammonium concentration.

A good agreement has been found between measured and computed values for NH3 and NH4 concentrations during the process.

The pH of the soil is the dominant factor controlling the extent of ammonia volatilization only when the soil's buffer capacity is high, or, when the concentration of ammonium in the soil is low. At high pH and high initial ammonium concentrations, the dominant factor controlling the reaction is the buffer capacity of the soil.
Estimated Association Constants for Some Complexes of Trace Metals with Inorganic Ligands
Authors: Mattigod Shas V. , Sposito Garrison
Published: July 2010

Chemical equilibrium studies of trace metals in soils by an ion‐association model require reliable data on thermodynamic association constants for various metal‐ligand complexes. Therefore, available experimental data at 25°C were compiled for complexes of the transition metal cations Mn2+, Fe2+, Nl2+, Cu2+, and Zn2+ with the ligands CO32‐, HCO3‐, SO42‐, HSO4‐, PO43‐, HPO42‐, H2PO4‐, Cl‐, and OH‐. However, experimental values of the thermodynamic association constants for many of the complexes were not available. This lack of information was alleviated by employing the theoretical model of Kester and Pytkowicz and the semiempirical models of Nieboer and McBryde, and Van Panthaleon Van Eck to make estimates of the as yet unmeasured association constants. These estimated constants were tabulated in a compact form along with the experimental values. This compilation of 100 association constants, although provisional, should prove helpful in a variety of studies on trace metal equilibria in soils until more reliable experimental data become available.
Pyrolysis‐Gas Chromatography‐Mass Spectrometry of Soil Humic Fractions: I. The Low Boiling Point Compounds
Authors: Martin F. , Saiz‐Jimenez C. , Cert A.
Published: July 2010

Pyrolysis‐gas chromatography‐mass spectrometry studies of fulvic and humic acids from different soils: Calcic Rhodoxeralf, Typic Xerochrept, Typic Chromoxeret, Andic Hapludult, Humic Haplorthod, Typic Haplorthod and a Canadian Orthic Humo‐Ferric Podzol were made. Samples were pyrolyzed at 700°C for 10 sec, and low boiling point compounds were separated in a Chromosorb 102 column. Peaks were identified with a mass spectrometer coupled to the gas chromatograph. Major components from soil humic acids were related to proteins, namely methane, ethene, ethane, propene, propane, butene, acetonitrile, benzene, pyridine, pyrrol, toluene, and phenol, and to polysaccharides, such as acetaldehyde, acetone, furan, methylfuran, 2‐butanone, and furfural. Soil fulvic acids gave pyrograms with major peaks of methane, ethene, acetaldehyde, acetone, furan, acetic acid, 2‐butanone, benzene, toluene, and furfural, which are characteristic for soil polysaccharides. Bromomethane, an unusual compound, was found in the humic fractions from podzolic soils.
Soil Inventory From Digital Analysis of Satellite Scanner and Topographic Data
Authors: Weismiller R. A. , Persinger I. D. , Montgomery O. L.
Published: July 2010

A soil inventory of Chariton County, Missouri was prepared using computer‐aided analysis of Landsat Multispectral scanner (MSS) data to determine how spectral soil maps produced by digital analysis of satellite MSS data can accelerate and improve the quality of the National Cooperative Soil Survey Program.

Landsat data collected on 15 Apr. 1974 were spatially registered at a scale of 1:24,000 and overlaid with ancillary data in the form of digitized township, watershed, and physiographic boundaries. The county was classified into 30 spectrally separable classes using computer‐implemented pattern recognition techniques. Approximately 64% of the county was identified as bare soil and was classified into 14 spectrally separable soil classes. The remaining 36% was classified as forest, pasture, and close‐grown crops.

The digitized boundary data allowed the computer to manipulate, compile, extract, and present spectral class information within topographic or political units. The physiographic boundaries were used to delineate three landscape positions of interest: (i) bottomlands, (ii) gently sloping uplands, and (iii) moderately steep uplands. These delineations allowed the computer to differentiate between spectrally similar soils which occur on distinctively different landscape positions. Spectral classes of soil were correlated with individual soil series and taxonomic classifications for both the bottomland and uplands units.

While a spectral classification of soils alone cannot distinguish between widely different soils exhibiting similar spectral responses, it can aid in identifying meaningful divisions of soils. By combining digitized ancillary data with MSS data, a more detailed delineation of soils can be provided as compared to information derived solely from MSS data. Further refinement of this technique will continue to increase the usefulness of satellite MSS data as an aid in soil survey.
Estimation of the Amount of Amorphous Materials for Characterizing Andosols
Authors: Kawai Kanji
Published: July 2010

An estimation method of amorphous inorganic materials in soils for characterizing andosols and tentative criteria for classification of andosols was proposed. Organic matter‐free fine earth is treated with 0.2N oxalic acid solution at 40°C for 6 hours under about 10,000 lux by a fluorescent lamp. The amounts of extracted silica, aluminum, and iron are highly correlated with values determined by the alternate dissolution method using hydrochloric acid and sodium hydroxide solutions.

Andepts have more than 50% of amorphous inorganic materials in the clay fraction as determined by the pipette method after treated by ultrasonic vibration. The soils, derived from volcanic ash and/or volcanic ash influenced or redeposited, containing < 50% of amorphous inorganic materials in the clay fraction and < 20% on an ovendry basis, are included in Andeptic subgroups.
Fate of Fertilizer Nitrate Applied to Coastal Bermudagrass on a Swelling Clay Soil
Authors: Kissel D. E. , Smith S. J.
Published: July 2010

The purpose of this study was to determine why N fertilizer recovery by Coastal bermudagrass (Cynodon dactylon L.) is lower on swelling clay soils than on coarse‐textured soils. The disposition of N fertilizer applied to Coastal bermudagrass in the field over two growing seasons was determined by applying 560 kg N/ha as Ca(NO3)2 tagged with 7.599 atom % 15N to a field microplot during 1974 and measuring various components of the N balance. Plant uptake of residual N was measured during 1975.

Forty‐nine percent of the applied N was recovered in harvested forage in 1974. About 40% of the applied N remained in the soil as residual N at the end of 1974. About 10% of the N was unaccounted for, indicating that denitrification losses were no more than 10% of the applied N. Most of the residual N at the end of the first growing season was immobilized N or was present in the root system of the grass. Immobilization is, therefore, a major factor causing low recovery of applied N by Coastal bermudagrass on swelling clay soils. Moreover, since only 17% of the residual N was recovered in forage during 1975 (7% of the N applied in 1974), most of the immobilized N was not available the following year.
Importance of the Organic Phosphorus Fraction in Extracts of Calcareous Soil
Authors: Abbott J. L.
Published: July 2010

Laveen clay loam soil samples were collected immediately following the harvest of forage sorghum [Sorghum bicolor (L.) Moench]. Two sets were prepared before growing turnips (Brassica rapa L.) as the test crop in the greenhouse. One set was without treatment and the other, to simulate winter and spring conditions, was incubated for 20 days after addition of N and dextrose. Phosphorus uptake by turnips and changes in soil P forms were positively correlated with corresponding measurements taken during the growth of the sorghum crop. With this as a basis, the effect appears to be similar to that which occurs in the field on the immobilization and mineralization of available P. Inorganic and total soil P were determined in extracts obtained by five procedures. Correlations among P uptake by forage sorghum, turnips, and soil P measurements indicated their value in predicting available P. Prediction values for two of the procedures were improved by including the extractable organic P with the inorganic P for the incubated soil. Results showed that (i) time of sampling, (ii) the crop to be grown, (iii) the method of extraction, and (iv) the means of converting organic P to a measurable inorganic form in the extract are of prime concern in deciding when to include extractable organic P in the P evaluation of a given soil.
Residual Effects of Calcium Silicate in Tropical Soils: I. Fate of Applied Silicon During Five Years Cropping
Authors: Khalid R. A. , Silva J. A. , Fox R. L.
Published: July 2010

A field experiment was conducted at the Kauai Branch Station to study the long‐term effects of calcium silicate applied to a Gibbsihumox soil. The fate of applied Si was determined during 5 years of cropping at one P (280 kg/ha) and three pH levels (5.5, 6.0, and 6.5). Plant uptake by the sugarcane plant (Saccharum officinarum L.) and ratoon crops, corn, (Zea mays L.), and seven harvests of kikuyugrass (Pennesetum clandestinum H.) accounted for 12 to 21% of the applied Si. Repeated extraction of profile samples taken at the end of 5 years with 0.1N acetic acid adjusted to pH 3.5 and containing 50 ppm P recovered 14 to 28% of the applied Si. There was no evidence that applied Si moved below the 30‐cm soil depth. This indicated that 57 to 72% of the applied Si remained in the soil in some fixed form not readily displaced by phosphate solution. Water‐soluble Si and plant uptake of Si decreased as pH increased while phosphate‐extractable Si increased as pH increased.
Oxygen Isotopic Ratios of Quartz from Wind‐Erosive Soils of Southwestern United States in Relation to Aerosol Dust
Authors: Sridhar K. , Jackson M. L. , Clayton R. N. , Gillette D. A. , Hawley J. W.
Published: July 2010

The oxygen isotopic ratios (expressed as parts per thousand relative to mean ocean water, SMOW, δ18O) of the quartz from 13 soils undergoing much wind erosion during the study period of 1972–1975 in four southwestern states and from comparison areas were determined. The δ18O for quartz from eight Texas (TX) and Arizona (AZ) soils range from 13.0 to 15.9 ‰. The quartz of the sands and silts coarser than 20 µm from three of the soils had δ18O values ranging from 13.1 to 15.1 ‰, characteristic of an ultimate igneousmetamorphic origin. The δ18O values increase greatly with decreasing particle size of quartz from three soils ranging from loamy fine sand to loam to clay in texture. The δ18O of the 1–10 µm quartz fraction (aerosol size) ranged from 19.2 to 20.2 ‰ (19.55 ± 0.28 ‰; ± sigma) for the thirteen soils most affected by dust storms. The higher values are suggestive of an admixture of some quartz crystallized at low temperature to quartz of high temperature origin. These results are not significantly different from the mean of 20.73 ± 1.82 ‰ found earlier for the same fraction from 30 shales of the midcontinental United States, but are 4 to 7 ‰ higher than those reported for New Zealand, Australian, and southern African soils. The 1–10 µm quartz from the comparison areas of TX and AZ soils in Fluvial materials further southeast and southwest has a δ18O mean of 17.7 ± 0.6 ‰, reflecting the influx of a slightly higher proportion of quartz from igneous sources than in the soils most affected by wind erosion. The oxygen isotopic ratios of 1–10 µm quartz from three Hawaiian soils and two sediments from Lake Waiau occurring at 3,970 m altitude on the Mauna Kea summit on the Island of Hawaii give a δ18O mean of 18.3 ± 0.2 ‰. Quartz of the above soils, including sandy, loamy, and clayey soils of southwestern United States, in addition to shales reported earlier, are source reservoirs of quartz having intermediate oxygen isotopic ratios characteristic of mixtures of two sources of quartz, one crystallized at high (e.g., δ18O = 11 ‰) and one at low temperature (e.g., δ18O = 30 ‰).
Pertinent Criteria for Describing the Dissolution of Gypsum Beds in Flowing Water
Authors: Keisling T. C. , Rao P. S. C. , Jessup R. E.
Published: July 2010

The equation for convective‐dispersive solute transport in porous beds and the continuity equation were used to derive a relationship describing the dissolution of gypsum beds in flowing water. The parameters involved in the derived relationship were: bed length, solution flow velocity, dispersion coefficient, mass transfer rate coefficient, and gypsum fragment size. The proposed relationship was compared with previously published data and shown to be valid. A potential practical field application of the procedure is presented.
Adsorption of Aldicarb By Clays and Soil Organo‐Clay Complexes
Authors: Supak James R. , Swoboda Allen R. , Dixon Joe B.
Published: July 2010

Adsorption experiments conducted with S‐methyl‐14C‐aldicarb resulted in what appeared to be negative adsorption (exclusion) of the toxicant on Ca− and Al− saturated montmorillonite clays. Calculated exclusion volumes indicated that aldicarb did not penetrate the interlamellar region. Aldicarb was excluded from at least the first 16 layers of water on external surfaces of montmorillonite. Positive adsorption occured with Ca− and Al− saturated illite and kaolinite clays. Equilihration of aldicarb solutions with one acid and two calcareous Vertisols, and with the organo‐clay complexes isolated from these Vertisols, produced negative adsorption isotherms for the acid and positive adsorption isotherm for calcareous adsorbents.
An Improved SMP Soil Lime Requirement Method Incorporating Double‐Buffer and Quick‐Test Features
Authors: McLean E. O. , Eckert D. J. , Reddy G. Y. , Trierweiler J. F.
Published: July 2010

The double‐buffer (DB) feature of the recently‐published Yuan method was applied to the Shoemaker‐McLean‐Pratt (SMP) method at several buffer pH levels, shaking times, and soil/solution ratios. The results, based on regression analysis of buffer‐indicated vs. Ca(OH)2‐titrated acidities, indicate that the widely used SMP single‐buffer (SB) method can be improved considerably by incorporation of DB, quick‐test, and mathematical‐adjustment features. However, the SMP‐SB method is still probably the most satisfactory compromise between simplicity of measurement and reasonable accuracy of results for soils of a wide range in lime requirement (LR). The SMP‐DB method with narrow soil/solution ratio and shorter shaking time gave excellent indication of soil LR when adjusted for incomplete reaction with the soil during the shorter “quick‐test” reaction time. This adaptation which looks very promising as an improved method (especially for use on soils of low LR where the SMP‐SB method is known to lack desired accuracy) is included as a recommended improvement of the SMP‐SB method.
Failure Sequence of Gully Headwalls in Western Iowa
Authors: Bradford J. M. , Piest R. F. , Spomer R. G.
Published: July 2010

A characterization of the failure sequence of gully headwalls and banks is necessary to predict gully erosion rates and to develop controls. A model is given for the sequential nature of gully growth in the thick loessial area of western Iowa. The failure sequence includes a popout or alcove failure near the toe of a near‐vertical wall, columnar sloughing of the overhanging material, and finally the transport of the eroded material downstream. The initiating failure at the base of the wall is a result of weakening of the soil material by wetting. The gully bank failure sequence and geometry in the western Iowa loess region is compared to gully erosion studies in the glacial drift region of northwestern Missouri and in the Piedmont of South Carolina.
Extraction of Soil Solution Using a Simple Centrifugation Method for Pesticide Adsorption‐Desorption Studies
Authors: Dao T. H. , Lavy T. L.
Published: July 2010

A simple and rapid centrifugation technique has been devised to extract small samples of soil solution from moist pesticide‐treated soils to allow measurement of the pesticide equilibrium concentration. Energy status of the soil water extracted was characterized by correlating the amount of centrifugal force applied, soil moisture content, and matric potential. By varying the size of soil samples and the centrifugal force applied, a sizable volume of soil solution (40 to 53% of the moisture content at or below 0.3 bar suction) was obtained from the soil. The pesticide equilibrium concentration of the soil solution remained relatively constant throughout the centrifugation process.
Leaching Characteristics of a Layered Field Soil
Authors: Starr J. L. , DeRoo H. C. , Frink C. R. , Parlange J.‐Y.
Published: July 2010

Two ponded flow experiments were conducted to study the leaching characteristics of a layered field soil, fine sandy loam over coarse sand, with a water table at a depth of 1.8 m.

In the first experiment a steel cylinder 1.8 m in diameter was driven into a soil to a depth of 3.6 m. Infiltrations of water and dye provided the means for direct observation of the effect of air entrapment upon the rates of infiltration as well as the primary pattern of water flow through the coarse subsoil. The rate of infiltration was observed to increase by nearly twofold when the entrapped air between the saturated surface layer and the shallow ground‐water table was vented directly to the atmosphere. Removal of the soil layers following infiltration of a dye solution showed that most of the infiltrating water moved through fingers ranging from 5 to 20 cm in diameter.

In the second experiment, chloride distributions at six depths were measured following the application of a pulse of 0.3N CaCl2 solution to the soil surface. Chloride movement for the 20− to 60−cm soil depths averaged about 50% slower than that determined from the average pore‐water velocity at the soil surface. In contrast to this relatively low rate of chloride movement, several salt pulses reached the 120− and 180−cm depths soon after or before reaching the 60−cm depth. This greatly increased flow rate corresponds to the observations in the first experiment where flow became unstable and the solute moved in fingers of flow below the 60−cm depth.
Linearized Moisture Flow with Loss at the Soil Surface
Authors: Lomen D. O. , Warrick A. W.
Published: July 2010

The general solution of a linearized moisture flow equation is derived for point and line sources whether buried or on the soil surface. The surface flux is taken to be proportional to the matric flux potential, which is consistent with the physical situation of small evaporative losses for dry soil and larger losses for wet soil. The fraction of water lost at the surface turns out to be identical for point and line sources and for the steady‐state case is [m/(2 + m)] exp(−ad) where m is the surface flux proportionality constant, d the depth of source, and α a constant from the assumed unsaturated hydraulic conductivity function. This fraction is plotted as a function of time for a fixed source depth. Also given are curves depicting the total water loss as a function of source depth. A generalized solution is derived for any type of source located in a horizontal plane.
Sorption and Availability of Molybdenum in Soils of Western Oregon
Authors: Jarrell W. M. , Dawson M. D.
Published: July 2010

Eight western Oregon soils were chemically characterized in an attempt to identify soil parameters affecting residual availability of fertilizer Mo to subterranean clover (Trifolium subterraneum L.). Amounts of “exchangeable” Fe and Al, “amorphous” Fe and Al, and “crystalline + amorphous” Fe in the soil were determined. As a measure of surface colloid OH‐ reactivity, the meq of H+ required to maintain a mixture of H2O2‐treated soil and 0.85N NaF at pH 6.8 was measured over a 25‐min period. Anion‐exchange‐resin‐extractable Mo (AER Mo) was removed from soil with a strongly basic anion exchange resin.

Molybdenum adsorption isotherms for each soil were determined by equilibrating soil samples at 25°C with Mo solutions ranging in concentration from 2 to 20 mg Mo/liter. The data for each soil conform to a Freundlich adsorption isotherm specific for that soil.

Molybdenum adsorption was related to the (NH4)2C2O4‐extractable Fe in the soil (R2 = 0.85**), but not to other fractions of extractable Fe or to extractable Al forms. The OH‐ released from each soil after 2 min of NaF treatment was correlated with NH4OAc‐extractable Al(R2 = 0.65**). Molybdenum uptake by subterranean clover grown in field experiments was significantly correlated with AER Mo (R2 = 0.17*). The correlation was significantly improved when two soils which behaved differently from the rest were statistically analyzed separately; the resulting correlations for the groups of two and six soils were R2 = 0.64** and R2 = 0.72**, respectively.
Effects of Solution Chemistry and Environmental Conditions on Ammonia Volatilization Losses From Aqueous Systems
Authors: Vlek P.L.G. , Stumpe J. M.
Published: July 2010

Laboratory studies were conducted to explain the wide variation in reported estimates of ammonia volatilization losses from N‐fertilized paddy fields. The ammonia volatilization capacity of a system was found to be equivalent to its alkalinity [NH3(aq), HCO32‐]. In solutions lacking alkalinity, loss of (NH4)2SO4 was limited, whereas loss of (NH4)2CO3 was essentially complete.

Ammonia loss from solution is best described as a consecutive reaction with opposing step. Ammonia volatilization per se followed first‐order reaction kinetics. The rate of ammonia volatilization is thus directly related to the concentration of aqueous ammonia and therefore to the concentration of ammoniacal N and pH. The rate of ammonia volatilization was severely restricted by limiting the movement of air above the water, as is often the case in the laboratory and field studies reported to date. Ammonia volatilization was enhanced by water turbulence and increased exponentially with temperature from almost nil at 0°C to approximately 20 mg N/100 cm2/5 hours at 46°C.
A Two‐Element Ceramic Sensor for Matric Potential and Salinity Measurements
Authors: Scholl David G.
Published: July 2010

A two‐element ceramic sensor was developed to produce optimum electrical response both to soil water matric potential and salinity. A spring‐loaded housing was developed for the elements for either drill‐hole or pit‐face placement. The sensors were calibrated under various matric potential, salinity, and temperature conditions. An initial field test with 72 sensors was conducted under irrigated coal mine spoil conditions. Laboratory and field results indicated reasonable instrument precision over a wide range of matric potential and salinity. The correlation between sensor output and water content in the field was best where the mean of several sensors was used.
The Use of Zero Point of Charge (ZPC) to Assess Pedogenic Development
Authors: Hendershot W. H. , Lavkulich L. M.
Published: July 2010

The pH at the zero point of charge (ZPC) has been used to characterize the electrochemical properties of soils. To date, most studies have focussed on soils high in oxides with low phyllosilicate content. The study reported here attempts to use ZPC determinations to characterize the surface charge characteristics of soils from a temperate region. Three soils were examined; these ranged in pedogenic development, as expressed by soil morphology, from a small accumulation of sesquioxides to a relatively high one. The soils were a Dystric Eutrochrept, a Typic Ferrudalf, and a Spodic Ferrudalf. With increased pedogenic development the ZPC became more clearly defined and approached the natural pH of the soil, and there was a decrease in the relative significance of the pH‐independent charge. The ZPC may be used as a measure of pedogenic development.
Nitrogen Sources for Hay Production on Flooded Meadows
Authors: Ludwick A. E. , Rumburg C. B. , Siemer E. G.
Published: July 2010

Three experiments were conducted over a 3‐year period to compare various urea materials and ammonium nitrate as N sources for hay production on flooded meadow sites. Each experiment was a complete factorial combination of fertilizer N sources and rates broadcast once in the spring on established forage prior to flood irrigation. Experiment 1 in Gunnison County consisted of ammonium nitrate (AN), urea (U), sulfur‐coated urea (SCU), and urea ammonium polyphosphate (UAPP) broadcast at rates of 0, 67, 134, 202, and 269 kg N/ha. A second season's data was collected to evaluate carryover N. Experiments 2 and 3 were conducted in Jackson County for a single season and consisted of AN, U, UAPP, and urea ammonium sulfate (UAS) broadcast at 0, 90, 179, and 269 kg N/ha.

Hay yields and N uptake were significantly increased by N fertilizer at each location; there was no significant response in hay yield or N uptake resulting from residual N in the second season of Experiment 1. Source of N did not influence hay yields nor N uptake. The N content of the hay was significantly influenced by the N fertilizer rate at two locations and the N source at one location. In general, hay yields and N uptake increased with increasing rates of fertilizer N. Fertilizer efficiency was low at all locations, ranging between 8.5 and 19.6 kg hay/kg N. Fertilizer N recovery was <30% for all treatments. Both efficiency and recovery of N tended to decrease with increasing N rates.