bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water Infiltration and Runoff under Rain Applications
Authors: Hachum Ahmed Y. , Alfaro Jose F. 
Published: July 2010

AbstractExperiments to verify the validity and to evaluate the performance of rain infiltration models based on extending the Green and Ampt approach are lacking in the literature. There are severe gaps between theory, validity, and practicality of these models. In this study, a physically‐based model for describing infiltration into a homogeneous deep stable soil profile with uniform initial water content distribution is presented. The derivation of the model is based on the concept of mapping the actual wetted soil zone into an equivalent rectangular saturated zone with constant effective hydraulic conductivity and capillary pressure head at the abrupt wetting front. The model takes into account the intial water mobility in the soil profile and predicts the system response under any rainfall pattern. The proposed model is further simplified, for practical purposes, by grouping three basic input parameters into a single parameter, the Surface Saturation Index.The validity of the model was tested and strongly supported by the results of laboratory experiments conducted on samples of three soils, two silt loams and a silty clay loam, under five different (variable and constant) water application rate patterns. It was found that the amount of runoff from a nearly symmetrical convex variable rainfall pattern was very close to that which resulted from its equivalent average constant application rate pattern, regardless of the significant differences between the times at which runoff begins and the characteristics of infiltration rates thereafter.
Rates and Patterns of Water Uptake in a Douglas‐Fir Forest
Authors: Nnyamah Joe U. , Black T. A. 
Published: July 2010

AbstractThe forest water balance was studied in a thinned (840 stems/ha) and an unthinned (1,840 stems/ha) Douglas‐fir forest [Pseudotsuga menziesii (Mirb.) Franco] during two consecutive summers. Soil water content was measured with the neutron meter. Soil water potential was measured with tensiometers and dew‐point hygrometers over a range of 0 to −15 bars. These data were used to compute water extraction rates and patterns for the root zone over a four‐week drying period. The results showed a gradual downward shift of the zone of maximum root water uptake as the soil dried. The fully developed root system of Douglas fir showed less hydrotropic response than the developing root systems of annuals reported in the literature. There was good correlation between water uptake rate and rooting density. During the drying period, water flux into the bottom of the root zone, estimated by the use of Darcy's law, increased from 8 to 15% of the evapotranspiration at the thinned site and from 2 to 8% at the unthinned site. Soil profile water depletion corrected for flux out of or into the bottom of the root zone agreed well with evapotranspiration computed from micrometeorological energy balance data. Water with‐drawal from trunk storage accounted for only 2% of the total evapotranspiration over the four‐week drying period.
Growth and Wood Properties of Longleaf Pine Following Silvicultural Treatments
Authors: Van Lear D. H. , Saucier J. R. , Williams J. G. 
Published: July 2010

AbstractThinning, fertilizer, and prescribed burning treatments were applied to a pole‐size longleaf pine (Pinus palustris Mill.) plantation in the Upper Coastal Plain of South Carolina. Thinning levels were 11.5, 18.4, 25.3 m2/ha of residual basal area, plus an unthinned treatment. Fertilized plots received 90 kg/ha P plus 168 kg/ha N. Half of the plots were burned prior to thinning and fertilization. Heavier levels of thinning produced a larger diameter response than fertilization, while burning had no effect during the two years following treatment. Diameter response to thinning resulted from increased formation of latewood, while the response to fertilization resulted from increased formation of earlywood during the first growing season after treatment. Because of these differences in growth response, thinning tended to produce wood of higher specific gravity while fertilization produced wood of lower specific gravity.
Nitrogen Response Relationships of Some Volcanic Ash Soils
Authors: Geist J. Michael 
Published: July 2010

AbstractMethods of assessing the N fertility status of ash soils and their relationship to plant parameters were studied in the greenhouse. Soils were collected from forested areas in the Blue Mountains of northeast Oregon. Highly significant regression relationships were obtained between soil N supply and N uptake of orchardgrass tops (R2 = 0.97) or top yield (R2 = 0.80) with responding ash soils. A polynomial regression model provided for organic, mineral, and fertilizer N supply sources. Soil organic N supply had a significant influence on plant performance over both narrow and broad ranges of fertilizer addition.
Characteristics of Silica Sorption and Solubility as Parameters to Evaluate the Surface Properties of Tropical Soils: II. The Index of Silica Saturation
Authors: Herbillon A. J. , Gallez A. , Juo A. S. R. 
Published: July 2010

AbstractSilica solubility of some Alfisols and Ultisols from southern Nigeria was studied. The concentration in soluble silica obtained after a 3‐day contact with a NaCl solution appears to be controlled by the most soluble silicate mineral present in the clay fraction. The index of silica saturation (ISS) is defined as the ratio of the amount of silica soluble in the NaCl extract and the index of silica reactivity of a given sample. ISS appears as a parameter which can be used to describe the surface properties resulting from the processes of silication and desilication taking place within the pedons and along the slopes in toposequences. In this study, ISS ranges from 9 × 10−4 to 685 × 10−4. The interest of ISS as a criterion for soil taxonomy is discussed.
Steady‐state Solute Convection in Two Dimensions With Nonuniform Infiltration
Authors: Batu Vedat , Gardner W. R. 
Published: July 2010

AbstractThe steady‐state unsaturated flow equation in two dimensions is solved for an exponential unsaturated conductivity using the Kirchhoff transformation. Streamlines, travel times, and isochrones are calculated for an infiltration rate which is a piece‐wise linear function of horizontal coordinate. Results are compared with the equivalent solutions for a saturated soil. In addition to solutions in dimensionless form, an example is presented for Plainfield sand. The results confirm that surface variations in infiltration rate may be propagated to a considerable depth, particularly in sandy soils. This may account, in part, for the variability in solute leaching frequently observed in the field.
A Neutron Activation Method for Determining Submicrogram Selenium in Forage Grasses
Authors: Cook K. A. , Graham E. R. 
Published: July 2010

AbstractNeutron activation as a method for the analysis of submicrogram amounts of Se in fescue and orchard leaves was evaluated. It was observed that the Se content of National Bureau of Standards orchard leaves was 0.078 ppm compared with the NBS reported value of 0.080 ppm Se. The relative standard deviation for the orchard leaves was found to be 5.3%.Following irradiation and nitric‐perchloric acid digestion, Se was extracted from a 4M HBr solution using benzene containing 1% phenol. The method is sufficiently sensitive to measure with accuracy 0.010 ppm Se in 0.250 g of material. The method is straightforward and accurate and requires the extraction of Se in benzene which is completely free of phosphorus.
Denitrification in Four California Soils: Effect of Soil Profile Characteristics
Authors: Gilliam J. W. , Dasberg S. , Lund L. J. , Focht D. D. 
Published: July 2010

AbstractThe effects of soil profile characteristics upon rate and products of denitrification were investigated using four soils in laboratory columns under steady‐state water flow conditions. A general relationship existed between soil texture and amount of denitrification. Soils with heavy textured subsoils readily reduced added NO3−. However, the soil with the lowest clay content had restricted water flow in the surface horizon and reduced the greatest amount of NO3−. The relationship between soil texture and denitrification is a result of the relationship between water flow and denitrification. It was concluded that any soil condition which impedes water flow will be positively related to denitrification and that spatial variability in denitrification is likely to be as great as observed variability in water movement.The ratio of N2 to N2O found during denitrification was extremely variable with measured values from 100:1 to 1:4. The low concentrations of N2O measured during denitrification occurred in soils where the denitrification was occurring deep in the soil profile, but there was no indication that this low concentration was a result of further reduction of N2O as N2O diffused through the soil profile. Our data indicate that it is currently not possible to accurately predict relative amounts of N2 and N2O which will be produced during most denitrification in soils, and that estimates of that N2O produced from agricultural lands have a large uncertainty factor.
Inhibition of Urease Activity by Heterocyclic Sulfur Compounds
Authors: Gould W. D. , Cook F. D. , Bulat J. A. 
Published: July 2010

AbstractThe inhibition of both jack bean urease and soil urease by several heterocyclic mercaptans was investigated. The following compounds not previously tested as urease inhibitors were found to be effective inhibitors of jack bean urease: 1,3,4‐thiadiazole‐2,5‐dithiol; 5‐mercapto‐3‐phenyl‐1,3,4‐thiadiazole‐2‐thione; and 5‐amino‐1,3,4‐thiadiazole‐2‐thiol. The disulfides of the latter two compounds were found to be very potent inhibitors of jack bean urease. The results are consistent with an inhibition mechanism involving a thiol‐disulfide exchange reaction between a disulfide and one or more of the sulfhydryl groups of urease. The results also imply that inhibition of urease by the heterocyclic mercaptans was due to trace amounts of the corresponding disulfides or polysulfides in the mercaptan preparations. A number of heterocyclic mercaptans, two disulfides, and a number of known urease inhibitors were evaluated as soil urease inhibitors, and the following compounds were the most effective: 1,4‐benzoquinone ∼ hydroquinone > 2,5‐dimethyl‐1,4‐benzoquinone ∼ catechol ∼ 1,3,4‐thiadiazole‐2,5‐dithiol ∼ 2,6‐dimethyl‐1,4‐benzoquinone.
Neutron Activation Analysis of Standard Soils
Authors: Koons R. D. , Helmke P. A. 
Published: July 2010

AbstractFour standard soils prepared by the Canadian Certified Reference Materials Project were analyzed for 25 elements to test for inhomogeneities within samples and to demonstrate the use of neutron activation for soil analysis. Five subsamples, weighing about 100 mg apiece, from each of two splits of each standard soil were analyzed. The precision of measurement as measured by the coefficient of variation was < 5% for 20 elements. No soil had more than four elements that differed significantly in concentrations between two splits at the 95% level of significance. Eight of the 12 differences that are significant occur for elements whose coefficient of variation is 2% or less.
Calibration Stability and Response Time for Salinity Sensors
Authors: Wood J. D. 
Published: July 2010

AbstractCommercially produced salinity sensors removed from field and lysimeter experiments lasting from 3 to 5 years were tested for calibration stability relative to the original factory calibration. Significant changes in calibration occurred in up to 14% of the sensors after 4 and 5 years of use. Response to a step‐change in salinity was also examined for commercial units in a field installation. Calculated response factors were lower than those found in a previous laboratory experiment. However, response was sufficiently rapid to assure accurate readings if changes in salinity occur in time intervals exceeding 5 days.
Fixation of Iron Applied as FeEDTA: Effect of Calcium Concentration and Soil Solid Phase
Authors: Lahav N. , Zipori I. 
Published: July 2010

AbstractIron fixation from FeEDTA was measured in three soils at various water contents and Ca concentrations as a function of time for periods up to 30 hours, using a batch technique. In the three soils under study the general pattern of the fixation reaction can be described as a first‐order reaction if adsorption is assumed to be much faster than fixation reaction. The rate constant is markedly affected by Ca concentration: in Rehovot sand and Nazaret clay loam (0 and 61% CaCO3, respectively) the reaction rate constant increases sharply as added Ca increases from 0 to 5 mM, followed by a moderate and more or less linear increase up to Ca concentration of 100mM. In Zophar sandy loam (69% CaCO3), the reaction rate constant shows a maximum at Ca concentration of 50mM and then decreases.In Rehovot sand and Nazaret clay loam the fixation process can be described by two independent first‐order reactions taking place simultaneously on the solid phase surface and in the liquid phase. Zophar sandy loam does not fit this model. It is suggested that the solid surface area affects the fixation reaction in addition to the effects of pH and Ca concentration.The effect of Ca on Fe‐FeEDTA fixation is discussed in connection to average and local Ca concentrations. High Ca concentrations near the root surface, formed due to transpiration stream, constitute a “chemical barrier” for the movement of Fe‐FeEDTA toward the root.
A Century of Soil Development in Spoil Derived from Loess in Iowa
Authors: Hallberg George R. , Wollenhaupt Nyle C. , Miller Gerald A. 
Published: July 2010

AbstractDuring the past century well‐drained soils have formed in leached loess spoil materials under prairie vegetation along railroad cuts in Iowa. The spoil material was deposited on an existing Tama Variant soil which reveals the effects of 100 years of burial.In 100 years' time a 31‐cm A horizon has developed in the spoil, available phosphorus recycling has been measured, and the translocation and accumulation of illuvial clay and fine silt has occurred. The organic carbon content reached a maximum of 2.6% and exceeds 0.58% to depths of 40 to 46 cm. This 100‐year‐old A horizon, however, does not meet the color criterion for a mollic epipedon. Organic carbon content seems to build up rapidly in the first 30 to 50 years of soil development. After this time a slower more steady‐state rate of increase seems to take place.In 100 years' time the buried soil shows a 1% decrease (from 2.6 to 1.6%) in organic carbon in the upper 20 cm. Most of this difference resulted from the degradation of fibrous organic matter after burial. Accompanying this loss of organic matter is an increase in bulk density, which has impeded soil water movement. This density contrast has enhanced the accumulation of illuvial clay and fine silts in both the lower portion of the 100‐year‐old soil and in the buried A horizon.
Ionic Composition of Forest Soil Solutions and Effects of Clearcutting
Authors: McColl J. G. 
Published: July 2010

AbstractSoil solutions were sampled with porous‐cup suction devices during a rainy season (December 1974–May 1975) from adjoining uncut and clearcut Eucalyptus globulus forest areas in the Berkeley hills, California. Concentrations of K+, Ca2+, Mg2+, NO3‐, HCO3‐, and pH and specific conductance were lower in the clearcut. The high exchange capacity of the clay‐loam soil, the limited amount and duration of rainfall, and the removal of slash and litter from the clearcut were factors contributing to these results which differ from those of similar studies of the effects of clearcutting elsewhere.The relative proportions of Na+, Cl‐, and SO42‐ were higher, and those of K+, Ca2+, NO3‐, and HCO3‐ were lower in the clearcut compared to the forest; the proportions of Mg2+ were the same. The relative ionic composition of soil solutions in the clearcut resembled that of the acid rain (pH 5.0). The higher proportion of HCO3‐ in the forest was due to throughfall inputs, root respiration, and decomposition of the forest floor. No NH4+ was detected in soil solutions from either area.Concentrations of most ions were correlated between and within soil horizons, although K+ was an exception due to clay fixation. During anaerobic conditions, Mn and Fe and associated Cu and Zn were mobilized in the soil solution.Increased quantity of soil water following clearcutting resulted in increases in total amounts of most ions in solutions in the lower portion of the profile in the clearcut, compared to the uncut forest.
Effectiveness of Rhizobium trifolii Populations Associated with Trifolium subterraneum L. in Southwest Oregon Soils
Authors: Hagedorn C. 
Published: July 2010

AbstractIndigenous Rhizobium trifolii populations were found to nodulate Trifolium subterraneum L. (c.v. Mt. Barker) but were largely ineffective or poorly effective in nitrogen fixation with this host. The rhizobia were isolated from numerous locations in southwest Oregon which contained subclover stands of widely varying quality. Rhizobium populations were greater in soils containing subclover stands while smaller populations were detected both in soils which had previously contained a subclover stand and those soils which had never been planted to subclover. Regression analysis of soil and rhizobia data showed significant correlations between the size of the rhizobial populations, the degree of fineness of texture (% silt + % clay) and the organic matter content while effectiveness was associated with the level of base saturation and the content of exchangeable bases. The requirements for a high quality inoculum in the presence of large ineffective populations and the agronomic implications for increasing subclover production are discussed.
Irrigation Water Salt Concentration Influences on Sediment Removal by Ponds
Authors: Robbins C. W. , Brockway C. E. 
Published: July 2010

AbstractIrrigation water salt concentration effects on sediment pond efficiency were investigated to demonstrate the necessity of considering the salt concentration in the irrigation waters when designing sediment retention ponds. The influence of dissolved salt was determined by adding concentrated CaCl2 solutions to three ponds and then measuring electrical conductivities and sediment concentrations at the pond outlets. Increasing the salt concentration increased the sediment removal efficiencies when the retention time in the pond exceeded 1 hour or the inflow sediment concentration exceeded 500 ppm for the three soils studied. Adding salt to laboratory soil sample suspensions increased the settling rates for the two soils studied. That data indicate that the salt concentration in irrigation water is an important factor in determining sediment pond size and retention time. Using pond design criteria obtained from sediment ponds receiving water of a given salt concentration to design ponds that will receive water with a different salt concentration should include adjustments for salt concentration differences. A simple laboratory test is suggested to predict which soils will respond to irrigation water salt concentration changes that are likely to result in sediment pond efficiency changes.
A Simple Chemical Method for Evaluating the Agronomic Potential of Granulated Phosphate Rock
Authors: Chien S. H. , Hammond L. L. 
Published: July 2010

AbstractA simple, chemical method which does not involve shaking the sample and which employs an H‐resin was used to evaluate the solubility of two granulated phosphate rocks over a range of granule sizes. It was found that the solubility decreased drastically as the granule size increased from the average diameter of 0.05 mm to 1.00 mm. The conventional citrate extraction method which involves shaking the sample cannot be used in this case because the granules disintegrated upon being shaken and this results in essentially the same solubility value being recorded for all samples regardless of the granule size. A highly significant linear relationship between the drymatter yield of corn (Zea mays L.) (6 weeks in greenhouse) and the solubility of the granulated rocks suggests that the proposed H‐resin method can be used to predict the potential of granulated phosphate rock for direct application.
Water Relations of Fritted Clay
Authors: van Bavel C. H. M. , Lascano R. , Wilson D. R. 
Published: July 2010

AbstractExperiments and calculations were performed to characterize the water relations of fritted clay, a material which has been found suitable for growing experimental plants. Its dry bulk density is 0.67 kg/liter, particle density 2.50 kg/liter, total porosity 0.73, and saturated hydraulic conductivity 9.5 × 10−4 m/sec. The desorption relation was measured and the unsaturated hydraulic conductivity as a function of water content was calculated. Much water drains from the saturated material by gravity. After drainage from commonly used containers, the material holds 0.31 by volume of plant‐available water, and has an air‐filled porosity of 0.28. Its water relations are excellent for plant growth purposes.
Relation Between Rheological Properties and Dry‐state b Dimension of Various Na‐smectites
Authors: Margheim J. F. , Low P. F. 
Published: July 2010

AbstractThe liquid limits of pastes of five different Na‐smectites were determined with the conventional liquid‐limit device. In addition, the penetration rate of a Teflon cone into each paste was determined at different water contents by means of a precision penetrometer. The water content at which a curve of penetration rate versus water content showed maximal curvature was called the “critical” water content. Both the liquid limit and “critical” water content were shown to decrease as the b dimension of the Na‐smectite increased. Since recent work has shown that the specific surface area of a Na‐smectite depends on its dry‐state b dimension, plots were made of the liquid limit and critical water content against specific surface area. They showed that both indicators of consistency increased curvilinearly with specific surface area. However, at a given state of consistency, the interparticle distance was not the same in the different smectite‐water systems but depended on the b dimension. Reasons for these findings were discussed in relation to the theory of plastic flow.
Chemical Characterization of the Gaseous and Liquid Environments of Subsurface Drain Systems
Authors: Meek Burl D. , Grass Luther B. , MacKenzie Arnold J. 
Published: July 2010

AbstractChemical composition of subsurface drain effluents was determined in the field as a function of location (various depths and soil textures), entry point of the solution into the drainpipe, and distance from outlet (with or without a water trap). Liquid samples were analyzed for Fe, Mn, NO3‐N, HCO3, organic carbon, electrical conductivity, pH, and dissolved oxygen, and gas samples were analyzed for O2 and CO2.Manganese ranged from < 0.1 to 6.1 ppm and Fe ranged from < 0.1 to 14.2 ppm which illustrated the wide range of oxidation‐reduction conditions present in the soils drained by subsurface drain lines. Chemical composition changed little during the season.Water entering the upper portion of the drain lines was lower in Mn, which was the result of short flow paths through soil zones with higher O2 levels, than the water moving through longer flowlines which entered the bottom of the drains. The solutions in the drain lines were undersaturated with respect to the drain line atmosphere, which indicated that O2 flows downward through the drain trench backfill. This is an important factor in the oxidation of Fe and Mn in subsurface drain lines. However, longitudinal movement of O2 into drain lines, via the outlets, is a minor factor contributing to the precipitation of Fe and Mn and does not account for the extensive amount of precipitation of Fe or Mn within the drain system.