bluuebunny/crossref_metadata_2025_split huggingface dataset:
Steady Infiltration from Sources at Arbitrary Depth
Authors: Raats P. A. C. 
Published: July 2010

AbstractThis discussion of steady infiltration is based on the assumption that the hydraulic conductivity is an exponential function of the pressure head. The solution for infiltration from a single point source at arbitrary depth is presented. On the basis of this solution, J. R. Philip's superposition theorem for surface sources is generalized to an arbitrary distribution of sources at arbitrary depths. General expressions for the pressure head, the total head, and the components of the flux are also given.
Further Evidence for the Inability of the Kjeldahl Total Nitrogen Method to Fully Measure Indigenous Fixed Ammonium Nitrogen in Subsoils
Authors: Meints Vernon W. , Peterson Gary A. 
Published: July 2010

AbstractThree methods of Kjeldahl total N determinations in soils were compared. Method 1 involved a pretreatment of the soil with a HF‐acid mixture and resulted in higher N values than methods 2 or 3 which involved a long period of digestion and a modification of a Gunning method, respectively. Differences in total N values obtained by the three methods were greatest for subsoils. The inability of methods 2 and 3 to measure all of the indigenous fixed NH4+‐N resulted in low N values and erroneously high C:N ratios in the subsoil.
Observed and Calculated Distribution of Lindane in Soil Columns as Influenced by Water Movement
Authors: Huggenberger F. , Letey J. , Farmer W. J. 
Published: July 2010

AbstractObserved and calculated distributions of lindane in soil columns of infiltration experiments were compared. Three mineral soils with different organic matter contents and particle size distributions were used in the study. The adsorption coefficient (K′) and rate of adsorption (α) were determined in independent experiments. As predicted by the theory, application of a greater amount of lindane to the soil surface increased the concentration of lindane but did not influence the depth of penetration. Under leaching conditions, the depth of water penetration divided by K was a good estimate of the observed depth of maximum concentration of lindane. The theory failed in general to predict the shape of the distribution curve of lindane.
Adsorption and Desorption of Diuron as a Function of Soil Properties
Authors: Mustafa M. A. , Gamar Y. 
Published: July 2010

AbstractThe study was conducted to determine the properties of 12 arid‐zone soils low in organic matter (0.1–1.7%) that are responsible for the adsorption and desorption of diuron [3‐(4,4‐dichlorophenyl)‐1,1‐dimethylurea]. Statistical analysis rendered r2 values for diuron adsorbed in relation of CEC, specific surface area, and organic carbon percentage equal to 0.785, 0.754, and 0.476, respectively. It was concluded that CEC or specific surface area can account for the variability of diuron adsorption in arid‐zone soils.Variability of diuron desorbed was basically due to diuron initially absorbed (r2 = 0.864). Again desorption could be predicted from specific surface area (r2 = 0.846) or CEC (r2 = 0.828) and not from organic carbon percentages (r2 = 0.372). Multiple regression analysis did not practically improve the linear relationship obtained from adsorption and desorption.
Stabilization of Amino Sugar Units in Humic‐Type Polymers
Authors: Bondietti E. , Martin J. P. , Haider K. 
Published: July 2010

AbstractStudies were conducted on the stabilization of amino sugar compounds against microbial degradation by the nucleophilic addition of the amino group to the aromatic nuclei of quinones. In accord with previous respirometer studies with amino acids and peptides, the presence of glucosamine or chitosan (polyglucosamine) increased O2 uptake in reaction mixtures of phenolics undergoing enzymatic or autoxidative polymerization. Model humic acids were prepared by enzymatic or autoxidative polymerization of mixtures of phenols commonly found to occur in soil or fungal humic acids. Labeled 14C glucosamine and chitosan were incorporated separately into these model polymers and the stabilization of the carbohydrate C against microbial attack in soil studied. For comparative purposes, peptone was also incorporated into model polymers. During a 12‐week soil incubation period 15–23% of the 14C activity of the glucosamine model polymers was evolved as CO2, whereas over 70% was evolved when glucosamine was added to the soil alone or mixed with a preformed model polymer. Four to 11% of the polymers incorporating peptone decomposed during this period. During an 8‐week period, 53% of the chitosan was lost as CO2 when added alone but only 31% of the chitosan which had been incorporated into the model humic polymer was lost. From 5–15% of the 14C activity in the glucosamine‐phenol model polymers could be solubilized by a 24 hour, 100C, 6N HCl hydrolysis. Residual 14C activity was distributed among all soil humus fractions after the incubation period. Infrared spectra were obtained of the model polymers alone, and incorporating glucosamine and peptone. Significant changes in absorbance occurred depending on the functional groups incorporated.
Effect of Phosphorus Fertilization on the Selenium Concentration in Alfalfa (Medicago sativa)
Authors: Carter D. L. , Robbins C. W. , Brown M. J. 
Published: July 2010

AbstractA study was conducted to determine the effect of P fertilization on the Se concentration in alfalfa. Adding P to the soil increased the Se concentration in alfalfa grown in the greenhouse on six of 14 soils from the northwestern United States. The Se concentration increase in alfalfa resulting from P addition was noted on some alkaline and some acid soils. Phosphorus addition increased the availability to alfalfa of both native and applied Se in the Portneuf silt loam. Applying 160 kg P/ha either as H3PO4 or concentrated superphosphate to Gooding sandy loam in the field increased the Se concentration in alfalfa from a level marginal for animal requirements to an adequate level.
Effect of Temperature on Pressure Head‐Water Content Relationship and Conductivity of Two Soils
Authors: Haridasan M. , Jensen R. D. 
Published: July 2010

AbstractA series of experiments was conducted in the laboratory to study the effect of temperature on pressure head‐water content relationship and on hydraulic conductivity as a function of water content and pressure head in two silt loam soils. Hydraulic conductivity was determined as a function of water content and pressure head at constant temperatures of 15, 25, and 35C by steady state and pressure plate outflow methods.The temperature dependence of pressure head‐water content relationship during pressure plate outflow could not be explained on the basis of changes in surface tension of air‐water interfaces alone. Pressure head‐water content relationship under steady state flow conditions was found to be different from that under transient flow conditions during pressure plate outflow. Desorption curves obtained at the three temperatures under steady state flow conditions did not reflect any temperature effects.Results of the steady state experiments were too variable to reflect any temperature dependence of hydraulic conductivity either as a function of water content or as a function of pressure head of soil water. Hydraulic conductivity as a function of soil water content was found to be more temperature dependent than as a function of pressure head of soil water in pressure plate outflow experiments. The increase in hydraulic conductivity at a given water content due to temperature rise is almost entirely accounted for by the decrease in viscosity of water.
Field Measurement of Unsaturated Hydraulic Conductivity by Infiltration Through Gypsum Crusts
Authors: Bouma J. , Denning J. L. 
Published: July 2010

AbstractField trials were made to test the use of gypsum crusts in the crust test method for measuring unsaturated hydraulic conductivity (K) in situ. Crusts consisting of mixtures of sand and gypsum were more stable and had more constant hydraulic properties than previously used crusts consisting of various puddled soil materials. Test results of four soil horizons are reported.
An Improved Construction Method for Platinum Microelectrodes
Authors: Mann L. D. , Stolzy L. H. 
Published: July 2010

AbstractAn improved construction method for platinum microelectrodes is described. The body of the electrode is completely encased in polyester casting resin. Electrodes constructed by this method are essentially leakproof and are especially suited for use in wet or waterlogged soils. Measurements obtained from this type of microelectrode are compared with others.
Determination of Total Phosphorus in Soils: A Rapid Perchloric Acid Digestion Procedure
Authors: Sommers L. E. , Nelson D. W. 
Published: July 2010

AbstractExtraction and colorimetric methods were evaluated for determining total P in soils. A procedure involving simultaneous digestion of 60 soil samples with perchloric acid and determination of extracted orthophosphate with an ascorbic acid method was evaluated. Analysis of diverse soils indicated that the proposed and conventional HClO4 digestion procedures yielded essentially the same total P values; however, both HClO4 methods underestimated total P by 1–6% when compared to Na2CO3 fusion. A comparison of colorimetric orthophosphate procedures indicated the method of Murphy and Riley (1962) was suitable for determination of orthophosphate following either HClO4 digestion or Na2CO3 fusion. Determination of total P in soils by tube HClO4 digestion and estimation of extracted P by the method of Murphy and Riley (1962) enables rapid and precise estimation of total P in a wide range of soils.
Effects of Lime and Boron on Brown‐heart, Leaf Tissue Calcium/Boron Ratios, and Boron Concentrations of Rutabaga
Authors: Gupta Umesh C. , Cutcliffe J. A. 
Published: July 2010

AbstractA greenhouse study involving four levels of lime and six levels of B, and a field study at two locations involving three levels of lime and five levels of B were conducted on rutabaga (Brassica napobrassica, Mill. var. ‘York’). Brown‐heart was more severe at high pH than at low pH under B deficiency conditions. The effect of lime on the appearance of B deficiency symptoms was a physiological effect in the plant rather than a chemical reaction in the soil. However, lime applications, generally decreased the B concentrations of leaf tissue.Calcium/B ratios in the leaf tissue were inversely related to the hot‐water‐soluble B content of the soil. Under field conditions, liming increased the Ca/B ratio of leaf tissue in most cases. Calcium/B ratios of 3,300 to 8,500 and B concentrations of 2 to 7 ppm in leaf tissue were associated with very severe brown‐heart condition. Leaf tissue Ca/B ratios of less than 400 and B concentrations greater than 40 ppm, when the roots began to enlarge were associated with roots free from brown‐heart.
A Reevaluation of the Ultrasonic‐Vibration Method of Dispersing Soils
Authors: Genrich D. A. , Bremner J. M. 
Published: July 2010

AbstractThe ultrasonic vibration method of dispersing soils was reevaluated by studies with 28 soils that differed markedly in pH (3.6–8.2), carbonate content (0–34% CaCO3 equivalent), texture (2–59% sand, 7–72% clay), and organic‐matter content (0.14–9.4% organic C) and included representatives of nine of the ten orders of the 7th Approximation. The results showed that ultrasonic vibration of soil‐water suspensions (2.5 ml of water/g of soil) by a high‐intensity probe‐type vibrator is an effective method for dispersion of, and yields stable suspensions with, a wide range of soils. They also confirmed previous evidence that tank‐type ultrasonic vibrators are not satisfactory for dispersion of soils and indicated that some reports of failure to achieve dispersion of soils by ultrasonic vibration can be attributed to use of inefficient vibrators.
Exchange Adsorption or Precipitation of Lead in Soils Treated with Chlorides of Aluminum, Calcium, and Sodium
Authors: Lagerwerff J. V. , Brower D. L. 
Published: July 2010

AbstractThe exchange behavior of Pb2+ present in small concentrations in kaolinitic, montmorillonitic, and illitic soils pretreated with Al3+ or Ca2+, and kept at a number of salt (Cl) levels, was in agreement with mass‐action law principles. The mean values of the Gapon exchange coefficient describing the distribution of ions between the adsorbed and solution phases in Cecil, Winsum, and Yolo soils were 0.31, 0.11, and 0.24 for Pb‐Al systems, and 4.13, 4.97, and 11.1 for Pb‐Ca systems. In Na+‐treated, alkalized soils, Pb precipitated. The solubility of the precipitate increased with decreasing pH and concentration of salt (NaCl). The solubility in solutions used for suspending the soil was less in the presence than in the absence of soil. This may indicate that the Pb‐soil complex is less soluble than the precipitate formed in solution, so that when soil is present the composition of the precipitate shifts toward a less soluble form. This would imply a multi‐component nature of the precipitate.
Persistence of Manure Phosphorus Availability in Calcareous Soil
Authors: Abbott J. L. , Tucker T. C. 
Published: July 2010

AbstractReappraisal of animal manure as fertilizer has shown manure to be an effective P source in calcareous soils. Correlations for data from cotton (Gossypium hirsutum) and barley (Hordeum vulgare) experiments indicated manure benefits to be largely the result of providing available P to the crop. Residual effects of manure P were measured by alfalfa (Medicago sativa) P uptake, yield and soil analyses following 4 years of cropping to cotton and 1 year of barley. Soluble P in Mohave clay loam manured at 22 metric tons/ha 4 years before sampling was above that of unmanured soil. Manuring at 2‐ or 3‐year intervals at 22 metric tons/ha appears to assure adequate P availability, while P availability from phosphate fertilizers may be negligible over the same period. The stable nature of manure organic matter, stimulation of microbiological activity and association of P with organic components of the soil may account for the resistance of manure P to processes removing phosphate fertilizer P from available forms.
The Microfabric of Petroplinthite
Authors: Eswaran H. , Mohan N. G. Raghu 
Published: July 2010

AbstractPetroplinthite or indurated lateritic concretions have been studied micromorphologically and also with the scanning electron microscope (SEM). It has been shown that the laterite is formed from a kaolinite mass by the absolute enrichment of iron oxyhydrates. In thin‐sections, the iron forms a vacuolar network; the vacuoles are composed of the original kaolinite and the network is formed by closely crystallizing goethite crystals. The goethite forms a strong, rigid framework giving the form and the hardness of the petroplinthite.SEM photographs of amorphous manganese and manganite are given. These are very localized occurrences. The few quartz grains in these laterites are etched and on the surface secondary quartz has formed.
Elemental Variability Within a Sampling Unit
Authors: Drees L. R. , Wilding L. P. 
Published: July 2010

AbstractTo determine the magnitude of lateral variability within an area of 1 to 2 m2, six profiles were sampled at 0.6 m‐intervals at each of three different sites representing loess, till, and outwash deposits. Elemental Ti, Zr, Fe, Ca, and K were determined by X‐ray spectroscopy for 50‐20µ and 20‐5µ fractions of selected horizons within each profile. Coefficients of variation within these deposits ranged from 1 to 13% for Ti, 4 to 20% for Zr, 3 to 20% for Fe, 5 to 13% for Ca, and 2 to 9% for K. The order of variability was loess ≤ till < outwash. No consistent differences in elemental variability were observed between size fractions or horizons (i.e. A, B, or C).Elemental data from a single horizon within a vertical profile will seldom permit mean estimates closer than ±10 to 20% (95% confidence interval) for loess and till deposits, and ±20 to 45% for the more variable outwash deposits. Three lateral subsamples within a given horizon would permit mean estimates of above elements within ±10% in loess and till but 20 subsamples would be required to achieve similar accuracies in some outwash deposits. Such data emphasize the need to multiple subsample horizons in a lateral dimension if mean estimates are to be accurate within 10 to 20% over an area approximating a pedon or sampling pit. The number of subsamples for a given horizon is a function of the element under consideration, nature of deposit, and precision of mean estimate desired.
Nutrient Availability in Desert Grassland Soils Under Mesquite (Prosopis juliflora) Trees and Adjacent Open Areas
Authors: Tiedemann Arthur R. , Klemmedson James O. 
Published: July 2010

AbstractA pot‐culture technique was used to calculate relative yields for N, P, K, and S as an index of availability of these nutrients in soil from under mesquite [Prosopis juliflora (Swartz.) DC] trees and from adjacent open areas on a desert grassland site. Arizona cottontop [Trichachne californica (Benth.) Chase], plains bristlegrass (Setaria macrostachya H.B.K.), and bush muhly (Muhlenbergia porteri Scribn.), all native perennial grasses which grow abundantly under mesquite, were used as test plants.Relative yields for N were up to 15 times higher in soil under mesquite trees than in nonmesquite soil, whereas the level of total N was only three times greater. The soil under mesquite trees apparently provides a more favorable environment for supply of N than nonmesquite soil.Relative yields for S in mesquite soil were three times greater than in nonmesquite soil and were proportional to the difference in total S between soils, indicating that S is supplied more slowly than N under mesquite trees.Phosphorus showed a slight, although significant, difference in availability between soils, but total P was the same in the two soils. A threefold higher level of organic matter in soil under mesquite probably contributes to increased availability of P.Differences in total potassium and its supply to test plants were not detected between the two soils.
Lithium Nitrate Fusion for Characterizing Layer Silicates in Disordered Soil Clays
Authors: Murthy A. S. Parashiva , Dixon J. B. , Kunze G. W. 
Published: July 2010

AbstractThe clay components in many Texas soils are difficult to identify using standard X‐ray diffraction techniques because of the diffuse and weak diffraction maxima corresponding to 001 spacings greater than 10A. After fusion of the clay fraction in LiNO3 for 18 hours at 300C, diffractograms with a strong diffraction peak at 18A were obtained. Mixed layered assemblages apparently cause the poor diffraction effects in untreated samples. Fusion with LiNO3 removes interlayer K+ allowing expansion to 18A of Mg‐saturated, glycerol solvated samples. X‐ray diffraction analysis after LiNO3 fusion clearly establishes the crystallinity of the clay and increases the sensitivity of the X‐ray diffraction method to the presence of dioctahedral 2:1 layer structured minerals.
Analysis of the Performance of an Improved Soil Heat Flux Transducer
Authors: Fuchs M. , Hadas A. 
Published: July 2010

AbstractSoil heat flux plates, made of a thermopile wound on a glass microscope slide, sandwiched between two anodized aluminum sheets were calibrated in a box designed to provide one‐dimensional heat flow of known flux density. The medium in the box consisted of various air dry soil separates of different texture and thermal conductivity. Calibrations were repeated under field conditions with two levels of soil moisture content. The variation of the sensitivity of each individual aluminum and glass heat flux plate in the different media was less than ±5% from the average, whilst the departure from the ideal sensitivity did not exceed 7%. Under the same experimental conditions the variation of the sensitivity of a commercial heat flux transducer made of low thermal conductive material was near ±15%, and differed by as much as 48% from the ideal value. The largest source of error was found to be the resistance to heat flow which appears at the contact between the soil and the transducer.
Soil Water Flowmeters with Thermocouple Outputs
Authors: Cary John W. 
Published: July 2010

AbstractThe construction and operation of two soil water flowmeters with microvolt outputs are described. One meter with a sensitivity of 0.1 mm of water flow per day is recommended for flux measurements in the surface meter of soil when the water matrix potential is greater than −0.8 bar. Calibration factors for three soils with different textures are presented as a family of curves. These curves may be interpolated for using the flowmeter in other soils, possibly without a loss of accuracy greater than the natural water flow variation from place to place in the field.The second meter with a sensitivity of about 0.5 mm per day will require some additional development and testing before it can be recommended for routine use. It does offer the possibility of making measurements at soil water matric potentials less than −1 bar and at relatively deep soil depths.The thermocouple flow transducer developed for the meters may be used to measure saturated soil water flow or other liquid flows as small as 1 ml/day.
Nitrate Concentrations in the Unsaturated Zone Beneath Irrigated Fields in Southern California
Authors: Pratt P. F. , Adriano D. C. 
Published: July 2010

AbstractNitrate concentrations in the drainage water of the unsaturated zone beneath the soil‐root zone were predicted from data for N inputs, N removal in harvested crops, and the drainage volume. Ratios of these predicted values to measured values were related to the volatilization losses or unaccounted‐for inputs expressed as a fraction of the excess N defined as the N input minus N removal in harvested crops. Volatilization losses or unaccounted‐for inputs were calculated as known inputs minus removal in harvested crops minus that removed from the soil‐root system by leaching.
An Oscillator Circuit for Automated Salinity Sensor Measurements
Authors: Austin R. S. , Oster J. D. 
Published: July 2010

AbstractAn oscillator circuit is described that enables automatic reading of salinity sensors and other a.c. conductivity cells by measuring frequency of oscillation. The oscillator frequency varies between 0.13 to 30 KHz and changes linearly with conductance in the range of 0.03 to 10 mmho/cm. The temperature sensitivity of the frequency of the oscillator is negligible between 8 and 31C. The calibration curves between frequency and conductance obtained with the oscillator circuit for both the electrical conductivity and thermistor elements of the salinity sensor are linear and readings can be obtained with lead lengths of several hundred meters.
Diffusion of Zinc in Soils: III. Relation to Zinc Adsorption Isotherms
Authors: Warncke D. D. , Barber S. A. 
Published: July 2010

AbstractThe rate of cation diffusion in soil is influenced by the buffering effect of the adsorbed cation on the solution concentration, dCl/dC, i.e., the change in solution zinc concentration with respect to change in the total diffusible soil zinc concentration. This effect was studied with Zn using four silt loam soils having a wide range of initial exchangeable Zn contents and cation exchange capacities (CEC). Zinc adsorption isotherms for these soils had slopes that increased as CEC decreased. The effective zinc diffusion coefficient, De, was measured at five Zn levels on each soil. Measured De, correlated with dCl/dC (r2 = 0.86). Values of De calculated from known values for volumetric moisture content, tortuosity, and dCl/dC were larger than observed De by factors of 5.5 to 18.2. Inclusion of CEC in a multiple regression of observed De with calculated De significantly increased r2 from 0.87 to 0.90. An additional soil factor related to CEC needs to be included to accurately calculate De values for Zn.