bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Temperature on the Gaseous Nitrogen Products of Denitrification in a Silt Loam Soil
Authors: Keeney D. R. , Fillery I. R. , Marx G. P. 
Published: July 2010

AbstractThe amount and relative proportion of N2 and N2O evolved from a nitrate‐amended surface soil under an atmosphere of He in the range of 7 to 75°C was examined. The objective was to evaluate the effect of temperature on N2O evolution and investigate the optimal temperature for denitrification. The soil had 2.43% organic C and pH of 6.8. Incubations were performed in all‐glass systems which were sealed throughout the incubation period. Denitrification products (N2O, NO, and N2) were determined periodically by gas chromatography using an ultrasonic detector. At the end of the incubation period, inorganic N remaining was determined.Above 15°C, the rate of denitrification increased with temperature, with an apparent optimum of 60 to 67°C. The percentage as N2O of the total (N2O + N2)‐N declined with time, but was still 44 to 50% of the gas produced at 16 days with the 7 and 15°C experiments. Nitrous oxide comprised up to 88% of the gas produced at 40°C after 2 days. At 50°C, most of the gas was N2O at one day, but at 60 to 67°C, N2O had disappeared by 1 day. Denitrification was still occurring at 70°C, but at a reduced rate. More than 85% of the N evolved at 70°C was as N2O. No denitrification occurred at 75°C.At 50 to 67°C, much more N was recovered as gaseous N than was initially present in the system as NO3‐N, and no (NO2‐+NO3‐)‐N remained at 4 days. These results are explained by the hypothesis that thermophilic Bacillus sp. (and perhaps others) rapidly reduces NO3‐ to NO2‐, with the NO2‐ reacting with oxidized N functional groups to form nitrogenous gases. This hypothesis was partially confirmed by experiments involving treatment of steam‐sterilized soil with NO2‐ at 40 and 60°C. Our results suggest that the commonly‐stated optimal temperature for denitrification may be too high for true biological denitrification due to the dominance of temperature‐dependent chemical reactions at >50°C.
Activity of Immobilized Pronase in the Presence of Montmorillonite
Authors: Griffith S. M. , Thomas R. L. 
Published: July 2010

AbstractThe activity of soluble and immobilized pronase in the presence of montmorillonite was examined using a differential spectrophotometric technique over a 100‐sec incubation period. On the basis of equivalent amounts of enzyme protein, the immobile enzyme had only 28% of the activity of the soluble pronase in the absence of clay. However, in the presence of clay, the immobile pronase was much less inhibited, retaining an average of 75% of its activity while the soluble pronase retained only 31% of its activity. The differential spectrophotometric procedure was satisfactory for monitoring the enzyme action in the presence of suspended clay.
Critical Levels of Soil‐ and Nutrient‐Solution Calcium for Vegetative Growth and Fruit Development of Florunner Peanuts
Authors: Wolt J. D. , Adams Fred 
Published: July 2010

AbstractThe separate effects of rooting‐ and fruiting‐zone Ca upon vegetative growth and fruit yield of ‘Florunner’ peanuts (Arachis hypogaea L.) were investigated in nutrient‐solution experiments where rooting and fruiting media were segregated. At low levels of rooting‐zone Ca, both vegetative and fruit growth were influenced by rooting‐ and fruiting‐zone Ca acting in concert. As root zone Ca was increased above the “critical” level for maximum vegetative growth, the plant changed from being almost fruitless to a well‐fruited plant.Results of nutrient‐solution studies in the growth chamber were verified in a greenhouse soil experiment using surface soil of a Dothan loamy sand (Plinthic Paleudult). Composite results from soil and nutrient‐solution experiments identified three separate “critical” solution Ca levels. Expressed as the activity ratio of Ca/total‐cations, the levels were: 0.10 for vegetative growth, 0.15 for flower fertility or fruit load, and 0.25 for pod fill. Substituting K for Mg in solution caused a lowering of the “critical” Ca levels.
Effect of Vegetation on the Morphology of Windsor Soils, Litchfield, Connecticut
Authors: Johnson Arthur H. , Siccama Thomas G. 
Published: July 2010

AbstractEastern hemlock (Tsuga canadensis) on outwash sand in Litchfield County, Connecticut produced a more acid forest floor and throughfall with a greater capacity to mobilize Fe than American beech (Fagus grandifolia) or white pine (Pinus strobus). White pine produced the least acid forest floor, and throughfall with the least capacity to mobilize Fe. These characteristics were reflected in the order of A2 and Bhir horizon thicknesses which was hemlock > beech > pine.
Effect of Tillage on Soil‐Water Movement During Corn Growth
Authors: Weatherly A. B. , Dane J. H. 
Published: July 2010

AbstractThe occurrence of drought during the growing season often limits the amount of soil water available for plant growth. The availability of soil water can further be limited if a hard layer exists not too far below the soil surface. Field experiments were therefore conducted on a Cahaba sandy loam soil (Typic Hapludult) to determine the effect of tillage practices on soil water movement during corn (Zea mays L.) growth. Four tillage practices, viz., conventional‐tillage‐without‐subsoiling, conventional‐tillage‐with‐subsoiling, no‐tillage‐without‐subsoiling, and no‐tillage‐with‐subsoiling, were studied on a soil with a plow plan. Soil water contents and soil water pressure heads were measured with a neutron probe and tensiometers, respectively. Water extraction by roots was determined by application of the integral form of the general transport equation for soil water. Soil water movement and water uptake were less for the conventional‐tillage‐without‐subsoiling treatment than for the other treatments. The two subsoiled treatments and the no‐tillage‐without‐subsoiling treatment indicated root penetration and soil‐water uptake below 50 cm.When soil water uptake patterns were compared with corn yield on a weight‐per‐ear basis, there was a direct, positive correlation between the amount of water taken up by the corn plants and corn yield.
Fluorine Distribution with Depth in Relation to Profile Development in Illinois
Authors: Omueti J. A. I. , Jones Robert L. 
Published: July 2010

AbstractFluorine content increases with depth, evidently in response to pH‐related absorption of F that has weathered from minerals in all size fractions of the upper solum. This relationship with soil colloids creates depth distribution characteristics of F that closely follow soil development trends that are especially well expressed by clay content. Fluorine attributed to organic matter in A and B horizons amounted to 9 µg/g of organic matter.
Nitrification Inhibition by N‐Serve and ATC in Soils of Varying Texture
Authors: Guthrie T. F. , Bomke A. A. 
Published: July 2010

AbstractAlthough numerous laboratory studies have demonstrated the effectiveness of certain nitrification inhibitors, many field studies have failed to show any significant crop response to inhibitor treatments. Most field studies to date have only evaluated N‐serve [2‐chloro‐6‐(trichloromethyl)pyridine], which cannot be conveniently applied with solid fertilizers due to its volatility. ATC (4‐amino‐1,2,4‐triazole) is a nonvolatile, water‐soluble nitrification inhibitor which can be easily coated onto solid fertilizers without volatilization loss. The objective of this research was to compare the effect of N‐serve and ATC on silage corn (Zea mays L.) production and nitrification rates in two soils (silt and loamy sand). Urea was coated with the inhibitors at a rate of 1% of active ingredient per weight of N and applied as a band or broadcast in the spring of 1977 and 1978. The NH4‐N/NO3‐N ratio in the soil was calculated for each sampling date as an indicator of inhibitor effectiveness. Neither inhibitor significantly affected nitrification when applied as a broadcast treatment to either soil. In the silt, both inhibitors were equally effective in delaying nitrification when banded, but in the loamy sand ATC had a five times higher NH4/NO3 ratio than N‐Serve 3 weeks following application. The effectiveness of N‐Serve persisted much longer in the silt (86 days) than in the loamy sand (23 days). This suggested that volatilization of N‐Serve severely limited its effectiveness in the loamy sand. There was no significant improvement in crop yields or N content due to inhibitor treatment in either soil.ATC is recommended for further field evaluation in conjunction with band‐applied solid fertilizers, particularly in coarse‐textured soils.
Summertime Flooding Effects on Alfalfa Mortality, Soil Oxygen Concentrations, and Matric Potential in a Silty Clay Loam Soil
Authors: Meek B. D. , Donovan T. J. , Graham L. E. 
Published: July 2010

AbstractSoil oxygen levels and soil water matric potentials were measured at the 15‐, 30‐, and 60‐cm depths in plots subjected to flooding times of 15, 25, 35, and 45 hours. A decrease to 6% O2 or less in the soil for > 24 hours resulted in substantial losses of alfalfa (Medicago sativa L.). Soil O2 content decreased more at the 15‐cm depth as compared with the 30‐ or 60‐cm depths because of higher matric potential. The critical matric potential that restricted O2 movement was about −11 cbars.
Solubility of Plutonium Compounds and Their Behavior in Soils
Authors: Rai Dhanpat , Serne R. J. , Moore D. A. 
Published: July 2010

AbstractThe solubilities of 239PuO2 (c) (crystalline) and 239Pu(OH)4 (am) (amorphous) under natural environmental conditions were determined. These data were then used to predict the (i) nature of the solid phases present in contaminated soils, and (ii) total concentration of Pu that can be expected in soil solutions when these Pu solids are present.Based upon solubility measurements, an estimated value of the log Kc (equilibrium constant at room temperature and an approximate ionic strength of 0.0045) for the dissolution of 239PuO2(c) [PuO2(c) ⇋ PuO2+ + e‐] was found to be −14.8. The estimated value of the log Kc for the dissolution of 239Pu(OH)4(am) [Pu(OH)4(am) ⇋ PuO2+ + 2 H2O + e‐] was found to be −12.8.Comparison of Pu concentration in equilibrium solutions of contaminated Hanford soils with the PuO2(c) and Pu(OH)4 (am) solubility lines suggested that Pu(OH)4(am) was absent from all the samples and that two of the samples contained PuO2(c). The presence of PuO2(c) was also confirmed by X‐ray diffraction of Pu particles isolated from one of the samples.
Effects of Lime, Silicate, and Phosphorus Applications to an Oxisol on Phosphorus Sorption and Ion Retention
Authors: Smyth T. Jot , Sanchez Pedro A. 
Published: July 2010

AbstractGreenhouse and laboratory experiments conducted with a clayey kaolinitic isohyperthermic Typic Haplustox from the Cerrado region of Brazil showed that CaCO3, CaSiO3, and previous P applications decreased P fixation and improved cation retention properties. The amendments were added at rates to replace 1 or 2× exchangeable Al, and P was applied at rates to provide equilibrium solution concentrations of 0, 0.05, 0.1, and 0.2 ppm P. Six months after application, CaCO3 and CaSiO3 at 1× exchangeable Al decreased the amount of previous P sorbed to provide 0.1 ppm P in solution by 18 and 24%, respectively. Previous P applications were more effective in decreasing P sorption than the amendments. A 540 ppm P rate decreased P sorption by 65% without amendments. The combination of amendments + 540 ppm P decreased P sorption by 85 to 91%. Fertilizer P recommendations based on soil solution levels for limed soils should be obtained with soil samples which have also been limed; otherwise the P requirement may be overestimated.Net negative soil charges increased by 11 to 47% with amendment applications and by 34% with 540 ppm P. The highest P and amendment rates doubled the net negative charge of this soil. Joint applications of P and soil amendments increased the negative charge and decreased the positive charge to a greater extent than when applied separately. Applications of both P and amendments made a major improvement in cation retention against leaching, but may increase anion leaching. P applications significantly increased soil pH and negative ΔpH values.
Enumeration, Effectiveness, and pH Resistance of Rhizobium meliloti Populations in Oregon Soils
Authors: Barber Lynn E. 
Published: July 2010

AbstractThe number of Rhizobium meliloti cells in the soil of alfalfa (Medicago sativa L.) fields and the effectiveness and pH resistance of strains of R. meliloti isolated from the soil were analyzed for their relationships to soil parameters. Soil samples were collected from three alfalfa‐growing areas of Oregon and analyzed for pH, exchangeable H, soil bases, P, N, and organic matter content, and cation exchange capacity. The number of infective R. meliloti cells was estimated using the plant‐infection assay. The nodulation effectiveness of each isolated R. meliloti strain was ranked using alfalfa growth response in tube culture and in comparison to uninoculated no N and N‐amended controls. The ability of each strain to initiate growth in media adjusted to pH values of 4.5, 5.0, 5.5, 6.0, and 6.5 was determined. The number of R. meliloti cells in the soil was greater with increased soil pH and with decreased age of the alfalfa stand. Although the average ability of the strains of rhizobia to initiate growth at low pH increased with age of the alfalfa stand from which they were isolated, the strain effectiveness decreased with stand age. Average effectiveness of the strains increased with inoreased soil percent base saturation and with decreased soil exchangeable H, N, and organic matter contents.
Scaling Soil Hydraulic Properties of a Heterogeneous Field
Authors: Russo David , Bresler Eshel 
Published: July 2010

AbstractField data for soil water characteristics and hydraulic conductivity have been scaled by two methods. The set of scaling factors (αj) determined by one method depends on soil water content. A correlation of r2 = 0.86 is obtained between scaling factors determined from soil characteristic data and those determined from hydraulic conductivity data. In the second method, the set of αj is normally distributed, and is highly correlated with αj obtained by the first method from water characteristic data at water contents near saturation. In one method the sum of squares, about an average curve, was reduced by 44 and 66%, for the water characteristics and hydraulic conductivities data, respectively, while 92 and 82.5% reduction was obtained by the second method, for the same respective data. The results suggest that in practice, a single stochastic variable may represent the hydraulic properties of a heterogeneous field.
Metal Binding Properties of Leaf Litter Extracts: II. A Bioassay Technique
Authors: Blaser P. , Landolt W. , Flühler H. 
Published: July 2010

AbstractA biological method is proposed to determine the maximum Cu binding ability and the conditional stability constant of leaf litter extracts. Free cupric ions reduce the 14CO2‐uptake of algae. In the presence of complex forming organic substances the observed depression of the relative CO2 uptake can be considered as a measure of the unbound ionic Cu concentration. Comparing the CO2‐uptake response function of solutions, with and without organic constituents spiked with variable amounts of Cu, yields a functional relationship between bound and free Cu. These functions can be interpreted with a sequential form of the Langmuir equation from which the maximum binding ability and the conditional stability constant are obtained. The presence of algae, modifies the complexing parameters, indicating that the values measured with nonbiological methods require careful interpretation when their significance in natural soils is considered.
Comparison of Extractants for Plant‐available Zinc, Cadmium, Nickel, and Copper in Contaminated Soils
Authors: Haq A. U. , Bates T. E. , Soon Y. K. 
Published: July 2010

AbstractThe objective of this study was to find a suitable extractant(s) for plant‐available metals in metal contaminated soils. Swiss chard (Beta vulgaris L. ‘Fordhook Giant’) was grown in greenhouse pots on 46 Ontario soils varying in degree of contamination with metals. The soils had been contaminated with metals to varying degrees over a period of years. After 40 days, the plants were harvested and Zn, Cd, Ni, and Cu concentrations were measured. Each soil was extracted with nine different extractants: aqua regia, 0.01M EDTA, 0.005M DTPA, 0.02M NTA, 0.5N CH3COOH, 1N CH3COONH4, 0.6N HCl + 0.05N AlCl3, (COOH)2 + (COONH4)2, and H2O. Zinc, cadmium, nickel, and copper concentrations in Swiss chard were correlated with the amounts of soil Zn, Cd, Ni, and Cu removed by each extractant. Of the nine soil extractants, CH3COONH4 was the best predictor of plant‐available Zn if only extractable Zn and soil pH were included as independent variables in a regression equation. Acetic acid was the best extractant for prediction of both plant‐available Cd and Ni when soil pH was included in the equation. Attempts to find a suitable soil extractant for plant‐available Cu were unsuccessful.
Effects of Nitrogen, Phosphorus, and Lime on the Forest Floor and Growth of Pole‐size Loblolly Pine
Authors: Van Lear D. H. 
Published: July 2010

AbstractChanges in the nutrient content of the forest floor and tree growth were studied after application of N P, and lime to a pole‐size loblolly pine (Pinus taeda L.) plantation in the South Carolina Piedmont. Nutrients move with varying speeds through the forest floor. Nitrogen broadcast at a rate of 56 kg/ha could not be detected in the forest floor after 10 months, but relatively large percentages of applied P, Ca, and Mg were retained for longer periods. Supplementing N with lime reduced the quantity of N in the F layer, probably because of higher nitrification and volatilization rates. The L layer of the forest floor, consisting of needles that fell after fertilizers and lime were applied, more readily reflected application of P, Ca, and Mg than did intact foliage. Dominant and codominant trees responded in the second growing season to treatments containing N. The duration of the response to the relatively light rate of N lasted from 1 to 3 years. Applying lime with N produced a positive response that was still evident after the fifth growing season. Applied P had no significant effect on growth.
Third‐order Integral Relation Between Sorptivity and Soil Water Diffusivity Using Brutsaert's Technique
Authors: Parlange J.‐Y. , Braddock R. D. , Lisle I. 
Published: July 2010

AbstractIntegral relationships between sorptivity and weighted mean diffusivity have been usually justified by numerical tests. Optimization provides a justification on more fundamental ground, when diffusivity increases rapidly with water content. The present paper presents a further improvement on the optimization result and its precision is discussed for two general classes of soil‐water diffusivities. The result should be useful to predict soil‐water diffusivity from sorptivity measurements, especially when it can be postulated that the diffusivity has a well‐defined (e.g., exponential) functional dependence on the water content.
Saturated‐Unsaturated Flow in Radial Directions Generated by an Injection Well
Authors: Babu D. K. 
Published: July 2010

AbstractThe paper investigates water movement under saturated‐unsaturated flow conditions. The flows result from a vertically placed line source that injects water at a constant rate into radial directions in space. Soil water diffusivity is assumed to vary as a positive, arbitrary power of water saturation. Singular perturbation methods are applied to derive an analytical form of the solution as a power series in the perturbation parameter. The solution so concentrated is freed from singularities and breakdowns, and is therefore uniformly valid at all points of space and time. Explicit formulae are derived for the location of the wetting front as well as for the transition face between saturated and unsaturated flow regimes. Several cases of the diffusion function and injection rates are illustrated in the form of graphs. Relevance of the analysis to problems of flushing out dissolved salts from soils is briefly commented on.
Determination of Nitrate and Exchangeable Ammonium in Soil Extracts by an Ammonia Electrode
Authors: Siegel R. S. 
Published: July 2010

AbstractA method for determination of NO3‐ in waters using an NH3 electrode was adapted for use with soils. Nitrate was determined in 1 N KCl soil extracts as the difference in NH3‐N concentration between aliquots treated with NaOH and Devarda's alloy to reduce NO3‐ and aliquots made alkaline without addition of Devarda's alloy. The rate of reduction of NO3‐ to NH3 was temperature dependent. The minimum recommended temperature for the procedure is 23°C. Rate of NH3 loss from solution and NH3 activity measured by the NH3 electrode increased with temperature.Nitrate‐N in extracts of nine Illinois soils determined with the NH3 electrode was highly correlated (r2 = 0.999***)3 with NO3‐‐N analyzed by the phenoldisulfonic acid method. Exchangeable NH4+‐N determined with the modified electrode filling solution was highly correlated (r2 = 0.99***) with exchangeable NH4+‐N determined by steam distillation. In addition to NO3‐, NO2‐ is reduced to NH3 by this procedure. Recovery of added NH4+, NO3‐, and NO2‐ was 97, 97, and 91%, respectively. Precision of NO3‐ and exchangeable NH4+ determinations were 0.2 and 0.1 mg/kg, respectively. The reagents used are relatively inexpensive and safe to handle, and reduction is carried out at room temperature. Only 20 ml of soil extract is required and soils containing 1 to 250 mg NO3‐‐N/Kg can be handled routinely. One worker can analyze 80 extracts/day.
Measurement of Swelling, Hydraulic Conductivity, and Shear Strength in a Multistage Triaxial Test
Authors: Parker J. C. , Amos D. F. , Sture S. 
Published: July 2010

AbstractThe multistage triaxial (MST) test described here measured swelling on saturation, hydraulic conductivity, isotropically consolidated‐undrained strength, and drained and undrained compressibility. Peak strengths were evaluated by application of a hyperbolic stress‐strain model and by extrapolation of stress‐strain curves to failure. Strength parameters obtained from MST and conventional triaxial (CT) tests agreed reasonably well for three compacted soils of widely varying properties. Both drained and undrained compression modulii from MST tests increased logarithmically with increasing confining pressure. Initial undrained compression modulii from CT and MST tests agreed fairly well, although there was a definite tendency towards reduced compressibility in the later stages of MST tests. Volumetric compressibilities during the drained phases of MST tests were markedly lower than those obtained in K0 compression tests.