bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption and Desorption of Diuron as a Function of Soil Properties
Authors: Mustafa M. A. , Gamar Y.
Published: July 2010

The 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

Studies 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

A 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

A 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

Field 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

An 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

Extraction 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

A 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

The 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

The 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

Reappraisal 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

Petroplinthite 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

To 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

A 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

The 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

Soil 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

The 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

Nitrate 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

An 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

The 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.
Effects of Phosphorus Application Rate, Soil Properties, and Leaching Mode on 32P Movement in Soil Columns
Authors: Logan T. J. , McLean E. O.
Published: July 2010

Movement of 32P‐labeled monocalcium phosphate was investigated in column experiments with P application rate, P‐fixation capacity, and mode and intensity of leaching as variables. Three soils of contrasting texture and P‐fixation capacity were studied. Leaching of P increased with P application rate and intensity of leaching. Constant head leaching resulted in greater movement of 32P out of the surface layer and greater accumulation in the leachate than intermittent leaching. In general, 32P recovered in the leachate was nonionic except in instances where maximum leaching occurred. Significant amounts of 32P were recovered in the leachate only with sandy loam soil and at the highest P application rate.
Complementary Ion Effects on Potassium, Sodium, and Calcium Displacement from Bi‐Ionic Bentonite and Illite Systems as Affected by pH‐Dependent Charges
Authors: McLean E. O. , Bittencourt V. C.
Published: July 2010

Bi‐ionic systems of bentonite and illite clay suspensions containing K‐Ca, K‐Na, and Na‐Ca were prepared in reciprocal saturation ratios at 100, 90, and 80% base saturations of bentonite and at 100, 80, and 60% saturations of illite. Each system was equilibrated with equal volumes of water, and then aliquots of each suspension were extracted with water, BaCl2, or HCl at 0.1 or 0.3 symmetry concentrations.

Displacement of a given cation varied greatly depending on the accompanying cation adsorbed to the exchange sites of the clays. This complementary ion effect, although occurring on both types of charge, was much greater when the exchange was from pH‐dependent charges. Thus, maximum complementary ion effects on K and Na displacement were at low saturations of the clays with these cations, while these effects on Ca displacement were greatest at high Ca saturations. Since BaCl2 generally displaced more basic cations from pH‐dependent charges than did HCl, the combined effects of higher valency of Ba and higher pH of displacement in BaCl2 than in HCl evidently were greater than the single effect of preferential H‐bonding to pH‐dependent charges.
Influence of Simulated Fall and Spring Conditions on the Soil System: III. Effect of Method of Simulating Spring Temperatures on Ammonification, Nitrification, and Microbial Populations
Authors: Campbell C. A. , Biederbeck V. O. , Warder F. G.
Published: July 2010

Experiments were carried out to determine (i) how different methods of simulating spring temperatures affect soil microbial activity, and (ii) the interactions between different types and amounts of added‐N and these temperature effects.

In soil amended with mineral‐N, ammonification (change in NO3‐N + NH4‐N) was inversely proportional to the amount of added‐N when incubated at 8.5C, but ammonification was not affected by amount of N when incubated at fluctuating temperatures. When peptone‐N was added to soil, ammonification was unaffected by the method of simulating spring temperature conditions.

In unamended soil and soil amended with 10 ppm NH4‐N, nitrification was greater at 8.5C than at square‐wave 14 to 3C. When peptone‐, NH4‐, or NO3‐N was added to soil, nitrification at 8.5C was generally equivalent to that at square‐wave 14 to 3C, but less than that at sine‐wave 14 to 3C. Where peptone‐N was added nitrification was > NH4‐N added > NO3‐N added.

In unamended soil, fluctuating temperature cycles were deleterious to the three major groups of microorganisms but were particularly detrimental to the nonsporeforming, gramnegative bacteria. Square‐wave fluctuating temperature was more deleterious than sine‐wave; the constant temperature regime was not deleterious. The deleterious effect of fluctuating temperatures was partially alleviated by addition of 25 ppm NH4‐N.

It was suggested that the protoplasmic materials released from the cells killed as a result of the fluctuating temperatures served as a ready source of N and energy substrate (much like the peptone amendment) for use by the surviving microbial populations.
Transformation of Propanil‐Derived 3,4‐Dichloroaniline in Soil to 3,3′,4,4′‐Tetrachloroazobenzene as Related to Soil Peroxidase Activity
Authors: Burge W. D.
Published: July 2010

Contrary to reports in the literature, no correlation was found between the peroxidase activity of five soils or the numbers of peroxidase‐producing microorganisms and the abilities of the soils to condense 3,4‐dichloroaniline (DCA) derived from the hydrolysis of N‐(3,4‐dichlorophenyl) propionamide (propanil) to 3,3′,4,4′‐tetrachloroazobenzene (TCAB). Amending the soils with an energy source increased the production of peroxidase extractable from the soil but decreased the amount of TCAB formed. It has been reported that a peroxidase‐producing fungus isolated from soil was capable of converting DCA to TCAB. However, peroxidase isolated directly from a soil of this study was incapable of converting DCA to TCAB. Apparently not all soil peroxidases catalyze the conversion.
Use of Physical Methods to Expand Soil Survey Interpretations of Soil Drainage Conditions
Authors: Bouma J.
Published: July 2010

Classification systems of soil drainage conditions are used in the soil survey program to characterize hydrodynamics of soils in the field and these data are used for soil survey interpretations. Estimates of soil permeability and internal soil drainage, based mainly on inferences made from morphological features, and an estimate of runoff are used in the Soil Survey Manual to determine the placement of a soil in one of seven drainage classes. Different soil moisture regimes are defined in the new soil taxonomic system in terms of measurements made in situ. These methods do not provide the quantitative data needed for predicting what soil behavior will be under environmental conditions that have changed temporarily or permanently. Complex numerical procedures and simple approximate physical methods, both requiring hydraulic conductivity and moisture retention data, can be used to calculate hydrodynamic soil behavior for a variety of simplified boundary conditions. Two approximate methods were applied to four Wisconsin soils in which measurements of hydraulic conductivity had been made in situ. This work revealed that two soils that had been placed previously in different drainage classes on the basis of differences in soil mottling, actually had comparable hydrologic properties.
Coincidence and Interference Corrections for Dual‐Energy Gamma Ray Measurements of Soil Density and Water Content
Authors: Mansell R. S. , Hammond L. C. , McCurdy R. M.
Published: July 2010

Coincidence and interference errors in the dual‐energy gamma ray attenuation method are discussed for simultaneous determination of water content and bulk density of soil columns. Collimated radiation from 300 mCi each of 241Am and 137Cs provides a high intensity beam comprised of 60 and 662 keV photons. Count rates measured by a single detector and a two‐channel gamma spectrometer were corrected for coincidence losses due to pulse‐resolving time. The lower energy channel counts were also corrected for Compton scattering of Cs radiation and for a counting loss attributable to a special coincidence interference.

Mass attenuation coefficients were determined for glass beads, water, and eight soil materials. Errors in soil water content measurement by the dual‐energy gamma attenuation method appears to be restricted to standard deviations of approximately 1% due to practical limitations in measurement precision of 60 and 662 keV attenuation coefficients for soil and water.
Theory of a Rectangular Gravel Envelope in Drainage Design
Authors: Kirkham Don , Selim M. Sami
Published: July 2010

A theory was developed to determine the radius of a circular drain which is equivalent to a square drain. A square drain is encountered in practice when a gravel envelope of square cross section is placed around a subsurface circular drain. The resistance of the gravel to flow was neglected. The square cross section of the envelope measured 4a2. The square drain tube was analyzed for two cases: (i) when an impermeable barrier was at great depth below the square drain tube center, and (ii) when the bottom edge of the square drain tube lay on a plane subsoil impermeable barrier. In both cases it was assumed that the length of 2a of the edge of the square drain tube was small compared with the distance from the drain's center to a water table over the drain and that the drain ran full. It is shown for Case 1 that an equivalent circular drain tube of radius 1.1772a may be used to replace the square drain tubes. If the square drains lie on the impervious layer, as in Case 2, the radius of the equivalent circular drain is 1.1037a.
A New Approach to Soil Testing: II. Ionic Equilibria Involving H, K, Ca, Mg, Mn, Fe, Cu, Zn, Na, P, and S
Authors: Baker Dale E.
Published: July 2010

Several experiments were conducted in an effort to modify a new approach to soil testing in which the equilibrating or testing solution contains each element for which the soil is being tested. This report includes results for modification which caused 15 soils to differ more with respect to test levels of Mn, Fe, Zn, Cu, S, and P without substantially changing their rankings for K, Ca, and Mg. Modifications included the incorporation of a preservative, a flocculating agent, a pH buffer, DTPA, and several additional elements to maintain a relatively constant activity coefficient for each element in different soils.

Results concluded that the adsorption equilibria soil test can be used successfully to test for several elements. The approach for calculating soil requirements is given for P. Although the test shows promise by indicating soil differences, additional calibration data will be required prior to routine use of the method.
Soil Characteristics of the Forest‐Prairie Ecotone in Northwestern Minnesota
Authors: Severson R. C. , Arneman H. F.
Published: July 2010

Physical, morphological, and chemical properties of a continuum of soil pedons expressing the developmental range from Haploboroll (Chernozem) to Eutroboralf (Grey Wooded) were studied in northwestern Minnesota. The abrupt nature of the forest‐prairie boundary and the abrupt change in physical, chemical, and morphologic properties of the soil pedons associated with this boundary do not reflect the gradual nature of the climatic or topographic gradients which occur across this area. The postglacial vegetation history for the area is documented and changes in soil development are related to this history.
Infiltration, Hydraulic Conductivity, and Resistance to Water‐Drop Impact of Clod Beds as Affected by Chemical Treatment
Authors: Gabriels D. M. , Moldenhauer W. C. , Kirkham Don
Published: July 2010

Chemicals were sprayed on large dry surface clods (8 to 20 mm) and small surface clods (2 to 8 mm) of a Clarion loam to test their effectiveness in preventing erosion during rainfall. The small clods were initially wetted with 15% water on a soil weight basis and mixed with bitumen emulsions. The large and small clods were subjected to a 6.35‐cm‐per‐hour simulated rainfall under controlled conditions in the laboratory. Simultaneously with the measurements of infiltration rate, determinations were made of (i) the starting time for initial runoff, (ii) energy needed to initiate runoff, (iii) runoff rate, (iv) total soil loss, and (v) final soil loss rate.

Surface applications of most of the soil conditioners on large clods applied at high enough rates kept the infiltration rate high and prevented runoff on a 9% slope. Polyvinyl alcohol and polyacrylamide prevented any soil loss during 90 min.

Surface applications with bitumen emulsions were also highly effective in preventing erosion of large clods but were less effective for small clods. When the bitumen emulsions were mixed with the small clods, the saturated hydraulic conductivity was very high. The infiltration rate was low because water would not enter the clod bed and stable clods were carried in the runoff water.
Priming Effect of 15N‐Labeled Fertilizers on Soil Nitrogen in Field Experiments
Authors: Westerman R. L. , Kurtz L. T.
Published: July 2010

Evidence of the “priming effect” on the uptake of soil N by additions of rather conservative amounts of fertilizer N was examined in data from two recently reported field experiments. In these experiments, urea and oxamide each labeled with 15N were compared on adjacent locations in successive years with ‘Sudax SX11’ Sorghum‐sudan hybrid (Sorghum sudanense) as the test crop. The priming effect in the first experiment was calculated from data from four cuttings during the first year and from a residual cutting during the second year. For the second experiment, data were used from the three cuttings harvested during the year the fertilizers were applied.

Additions of N fertilizer increased the uptake of soil N by 17 to 45% in the first experiment in 1966 and by 8 to 27% in the second experiment in 1967. In the residual cutting of the first experiment, increases in uptake of soil N ranged from less than 0 to 29%. The increase in uptake of soil N by the crops was speculated to be due to stimulation of microbial activity by N fertilizers which increased mineralization of soil N, thus making more soil N available for use by plants.
Effect of Forest Cover Removal on Depth of Soil Freezing and Overland Flow
Authors: Sartz Richard S.
Published: July 2010

Depth of soil freezing and overland flow were measured under four hardwood forest conditions in southwestern Wisconsin: woody vegetation cut and removed; all vegetation cut and removed; uncut forest with litter removed; and undisturbed forest. Removing only the litter and removing all the vegetation increased both soil freezing depth and overland flow. Removing only the woody vegetation decreased both. Frost‐depth means in a year of deep frost were 6 and 11 cm on the woody vegetation removed and undisturbed plots, and 19 and 35 cm on the all vegetation‐removed and litter‐removed plots. Overland flow values ranged from less than 1 cm on the woody vegetation‐removed plots to more than 7 cm on the all vegetation‐removed and litter‐removed plots. The increases in frost depth and overland flow appeared to be related to changes in soil bulk density and porosity.
Forest Windthrows and Their Influence on Soil Morphology
Authors: Armson K. A. , Fessenden R. J.
Published: July 2010

The variability in thickness of the O and A2 horizons was studied on a sandy loam forest soil in the Great Lakes‐St. Lawrence Region of southern Ontario. Horizon thicknesses were recorded in 1.3 cm (0.5 inch) classes for each 10.2 cm (4 inches) of horizontal distance on the faces of each soilpit. Soilpits were located both subjectively on windthrows and randomly in the study area. Thickness frequency distributions for O horizons were normal and for the A2 horizons Poisson‐like. Both were independent of recent fire history and sampling method. It may be inferred that the disturbance by windthrow is infrequent in relation to O horizon formation, but frequent relative to A2 horizon development. Microtopographic position had a slight effect; thicknesses in top positions being somewhat less than for bottom positions. Horizon distortions related to windthrow disturbance were recorded for only 19% of the soil profiles sampled.
The Simultaneous Effect of pH and Chloride Concentrations upon Mercury(II) as a Pollutant
Authors: Hahne H. C. H. , Kroontje W.
Published: July 2010

The mercuric ion, compared to other heavy metal pollutants, hydrolyzes at low pH values and forms soluble chloride complexes at low chloride concentrations. To evaluate the possible implications of such behavior in natural aquatic systems, Hg(II) hydroxy and chloride species distributions were calculated using pH and chloride ion concentrations as variables simultaneously. Range in pH values selected was from 2 to 9 to cover conditions encountered in acid mine drainages, rivers, all types of soil solution extracts, and sea‐water. In addition, a study was performed in which montmorillonite, illite, and kaolinite were equilibrated with different HgCl2 solutions. The range of HgCl2 concentrations in equilibrium solutions was 1.25 × 10‐4M to 0.005M.

Results of the calculations show that chloride complexes compete effectively with the hydroxy complexes of Hg(II). The chloride and hydroxy complexes may contribute appreciably to the mobilization of Hg(II). The mobility of Hg(II)‐hydroxide is limited by the intrinsic solubility of Hg(OH)2. At pH 4 and 5, chloride ion concentrations of 3.5 and 14 ppm, respectively, are sufficient for all Hg(II) to be in the HgCl2° form. At higher pH values, partial to complete mobilization is possible depending on the prevailing chloride and Hg(II) concentrations. The equilibria study with the clay minerals revealed that little or no Hg(II) was adsorbed. The chloride ion concentrations of the equilibrium solutions varied between 1.4 and 14 ppm and pH values ranged from 3.68 to 4.90.
Effect of Rainfall and Subsequent Drying on Nitrogen and Phosphorus Changes in a Dryland Fallow Loam
Authors: Campbell C. A. , Biederbeck V. O. , Warder F. G. , Robertson G. W.
Published: July 2010

36Chloride placed at 15‐ or 30‐cm depth in 15‐cm diameter cylinders of fallow loam was leached to at least 50 cm during and immediately following rainfall > 1.75 cm. As the soil dried following rainfall 36Cl moved upwards. Nitrate content of leachates from a lysimeter experiment corroborated the leaching aspects of the 36Cl expcriment.

In the 0‐ to 2.5‐cm segment of a second‐year fallow loam which was sheltered from rainfall, moisture was below the wilting percentage and NO3−N and bacterial numbers declined as the soil gradually dried out. In the 2.5‐ to 15‐cm segment, moisture was in the available range, yet moisture and NO3‐N changes were small.

In unsheltered fallow loam, NO3‐N production in the 0‐ to 2.5‐cm depth was primarily a function of soil moisture change: ΔNO3−N = −0.55 − 1.11 ΔM, (r = −0.94**), and ΔNO3‐N = −0.45 ‐ 0.56 ΔM, (r = −0.81*) in the second‐ and first‐year fallow, respectively; (M = % moisture and Δ = daily change). The increase in NO3‐N during drying seemed to be more a result of upward movement than of nitrification. There was a negative linear relationship between ΔNO3‐N and Δ bacteria in the 0‐ to 2.5‐cm soil segment. Sodium bicarbonate soluble inorganic P (IP) generally exceeded NaHCO3 soluble organic P (OP). In second‐year fallow, P was unaffected by environmental conditions. In first‐year fallow ΔIP in the 0‐ to 2.5‐cm segment was directly related to rainfall (r = 0.98**), to ΔM (r = 0.97**), and to Δ bacteria (r = 0.88**), and inversely related to ΔNO3‐N (r = −0.76*).
The Effect of Exclusion Volume on Potentiometric Nitrate Measurement
Authors: Gilmour J. T. , Scott H. Don
Published: July 2010

Data are presented which show that large anion exclusion volumes can occur when montmorillonitic soils, low in total salt, are extracted with water. Nitrate measurements on such extracts with the nitrate specific ion electrode reflect this exclusion volume induced error. A possible solution to the problem is suggested.
Evaluation of Water Flux Above A Deep Water Table Using Thermocouple Psychrometers
Authors: Enfield C. G. , Hsieh J. J. C. , Warrick A. W.
Published: July 2010

Deep water flow was evaluated in a Washington desert environment using hydraulic conductivity and potential gradients. Thermocouple psychrometers and temperature transducers were installed to depths of 94 m in the soil profile and used to measure the potential gradients. The hydraulic conductivity was calculated using a modified Millington and Quirk equation and the soil moisture characteristic curve. The thermal fluid diffusivity was calculated and used to estimate flow induced by thermal gradients. Under the conditions studied, a more refined analysis of the thermally induced flow is required to give a definite answer as to the direction of flow. It was concluded, however, if flow existed at this location, it was less than 1 cm/year.
Estimates of Potentially Mineralizable Soil Nitrogen Based on Short‐Term Incubations
Authors: Stanford George , Carter J. N. , Smith S. J.
Published: July 2010

Nitrogen mineralization potentials were determined for a large number of soils by a method involving determination of N mineralized after several consecutive incubations at 35C under optimum soil water conditions. The determination of N mineralization potential, No, based on the first‐order equation, log (No − Nt) = log No − kt/2.303, is laborious and usually requires incubation periods of 8 weeks or more. From the present study, involving soils from major agricultural areas throughout the United States, it was demonstrated that No could be estimated reliably from the amounts of N mineralized during 2‐week incubations following preliminary incubations of 1 to 2 weeks. From the above first‐order equation, No = Nt/(1–10‐kt/2.303). Hence, for a 2‐week incubation (t = 2), No = 9.77Nt (Nt = N mineralized in 2 weeks and k is the rate constant, weeks‐1). Estimates of No from short‐term incubations were similar to those derived after extensive periods of incubation. Preincubation of soils is required in order to decompose plant residues and for other possible reasons noted. Estimates of No from preliminary incubations are meaningless. The implications of No as a basis for predicting amounts of soil N mineralized under fluctuating temperature and soil water conditions are discussed.
Isotopic and Nonisotopic Estimations of Fertilizer Nitrogen Uptake by Sudangrass in Field Experiments
Authors: Westerman R. L. , Kurtz L. T.
Published: July 2010

Recoveries of fertilizer N in above‐ground portions of crops grown in field experiments were estimated by: (i) difference method; (ii) linear regression of total N in crops on rates of applied N; (iii) 15N isotopic tracer method; and (iv) linear regression of labeled fertilizer N uptake on rates of labeled fertilizer N. In order to evaluate the use of the isotope, these four methods were applied to data from previously reported experiments (Westerman, Kurtz, and Hauck, 1972) which involved two 15N‐labeled fertilizers (urea and oxamide) at rates of 0, 56, 112, and 168 kg N/ha. The test crop was Sudax (SX11) sorghum‐sudangrass hybrid (Sorghum sudanense) and harvests were made at approximately 30‐day intervals during the cropping seasons.

The difference method overestimated recovery of urea and oxamide nitrogen in sudangrass 35 and 31%, respectively, in 1966 and 23 and 35% in 1967 when compared to the isotopic tracer method. Similarly, linear regression of total N in crops on rates of N overestimated recoveries of urea and oxamide nitrogen 32 and 17%, respectively, in 1966 and 17 and 21% in 1967 when compared to linear regressions of fertilizer N in crops on rates of 15N labeled nitrogen. Isotopically‐labeled fertilizers are almost a necessity for estimating N recovery in many agronomic experiments.
Extractable Iron in Relation to Soil Age on Terraces Along the Truckee River, Nevada
Authors: Alexander Earl B.
Published: July 2010

Weathering and soil phenomena often serve as aids for correlating Quaternary deposits. An investigation was designed to determine if the ratio of acid oxalate to citrate‐dithionite extractable Fe, called the Fe ratio, has a definite age trend which might be helpful in deciding the age sequence of associated but noncontiguous Quaternary deposits. Iron was extracted from the subsoils of well‐drained Xerolls on eight adjacent terrace levels in a subhumid climate on the eastern side of the Sierra Nevada Mountains. Citrate‐dithionite treatment extracted 1.0 to 1.6% Fe from the less than 2‐mm fractions of the soils. The data suggest that the Fe ratio increases in the first several thousands of years of soil development, to 0.37 on the second terrace above the Truckee River, and then it decreases to a practically constant 0.18 in a few hundreds of thousands of years. Although the Fe ratio values are not sufficiently unequivocal to be used alone for placing associated Quaternary deposits in sequence, they may be useful supplements to other criteria.
Estimating Soil Erosion from the Redistribution of Fallout 137Cs
Authors: Ritchie Jerry C. , Spraberry James A. , McHenry J. Roger
Published: July 2010

The movement of fallout 137Cs from soils in three north Mississippi watersheds was found to be logarithmically (r = 0.89) related to potential soil loss as calculated by the Universal Soil Loss Equation. Analysis of other published data on 137Cs as well as the north Mississippi data also showed a significant (r = 0.95) logarithmic relation existing between soil loss and 137Cs loss from soils. This study indicates that it may be possible to calculate soil loss from the movement of fallout 137Cs in watersheds. Also it may be possible to calculate the movement of surface adsorbed nutrients like 137Cs in watersheds from soil erosion data.
Sampling Macro‐Organic Matter Profiles in Salt Marsh Plant Root Zones
Authors: Gallagher John L.
Published: July 2010

A device for sampling the root zones of marsh plants and a method for processing the resulting cores are described. Using these techniques, five stands of marsh plants were sampled and their macro‐organic matter profiles compared. The least total macro‐organic matter was found in the high vigor Spartina alterniflora Loisel. and the Distichlis spicata (L.) Greene root zones. Within S. alterniflora stands, the macro‐organic matter in the soil profile increased as vigor of the aerial portions decreased. Juncus roemerianus Scheele and short form S. alterniflora profiles were similar in shape and had the highest macroorganic matter content.
A Steady‐State Model of Isotopic Fractionation Accompanying Nitrogen Transformations in Soil
Authors: Shearer G. , Duffy J. , Kohl D. H. , Commoner B.
Published: July 2010

A steady‐state mathematical model of isotopic fractionation accompanying certain nitrogen transformations in soils is developed. The model takes into account ammonification, nitrification, and immobilization; and predicts that the 15N/14N ratios of nitrate and ammonium ion depend in part upon the ratio of the rates of immobilization and ammonification. The ratio of the rates of immobilization to nitrification under field conditions is unlikely to be the same as under the conditions of laboratory incubation experiments. Therefore, this prediction provides a possible explanation for differences observed between the 15N/14N ratio of nitrate extracted from soil cores and that of nitrate released during laboratory incubation of the same soils.

The model described is ammenable to experimental test. If verified, an expanded version of the model may be a useful aid in the study of nitrogen transformations in the field.