bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Bulk Density and Initial Water Content on Infiltration in Clay Soil Samples
Authors: Gumbs F. A. , Warkentin B. P.
Published: July 2010

Infiltration measurements were made on swelling clay soil samples packed into columns. Small increases in bulk density over the range 1.10 to 1.25 g/cm3 markedly decreased the rate of water movement. The magnitude of the effect was greater for confined samples than unconfined samples at all initial water contents. A 1‐cm compact layer in the profile retarded water movement if the soil was confined. In partially confined samples the soil in the compact layer would swell on wetting, and water movement was retarded only when the bulk density after swelling still exceeded the bulk density of the remainder of the column. Bulk densities below 1.05 g/cm3, and heat of wetting in partially confined samples with 0% initial water content produced nonlinear distance to wet front vs. square root of time relationships. Comparison of horizontal and vertical infiltration showed that under these experimental conditions gravity contributed significantly to water movement at high initial water content.
Phosphate Fixation by Aluminum in Plant Roots
Authors: McCormick Larry H. , Borden F. Yates
Published: July 2010

Although the exact physiological mechanism of Al toxicity is unknown, experiments have indicated that Al reduces the uptake of phosphates in plants. The suspected sites of Al‐phosphate interaction are within the root tissue and along the root surface. The present investigation was designed to identify by photomicrographic techniques the sites of phosphate fixation by Al within plant roots. Following pretreatment immersion of barley (Hordeum vulgare) and poplar (Poplus sp.) in solutions containing various concentrations of Al and phosphate, whole roots and sections of root tissues were selectively stained by using a modified Mo blue method to detect the location of phosphate. Color photomicrographs of the root section showed a definite interaction of Al and phosphate in the root cap and in the epidermal and cortical regions extending back from the root tip 1 to 5 mm. The Al‐phosphate interaction appeared to be associated with the cell wall and cytoplasmic membrane of the epidermal and cortical cells. Results also indicated that Al adsorbed by the root surface or in the intracellular free space may be capable of immobilizing phosphate present in the root tissue or in the external substrate.
Potassium Selectivity in Certain Montmorillonitic Soil Clays
Authors: Carson C. D. , Dixon J. B.
Published: July 2010

Potassium selectivity (kG) was relatively constant when K‐saturation exceeded 15% for soil clays. As K‐saturation decreased from 15% or less, depending on the soil and clay fraction, kG increased exponentially. The 2 to 0.2µm clay fractions had high kG values to about 15% K‐saturation, apparently due to dioctahedral mica and vermiculite. Potassium selectivity for 0.2 to 0.08µm and <0.08µm soil clay fractions was below kG = 4.5 for about 85% of the exchange sites which corresponds to the montmorillonite contribution to cation exchange capacity (CEC) in these soil clays. Mica content correlated well with kG at a point near the steep part of the selectivity curves indicating the influence of small amounts of mica and possibly associated vermiculite on kG values. High kG values that occur over several percent K‐saturation in coarse soil clay fractions indicate that this fraction is more important than the more abundant finer fractions in controlling kG values and presumably K+ availability to plants. Increases in kG values for reference montmorillonites where only a few percent K‐saturation exists are attributed to mica and possibly vermiculite impurities. Dioctahedral mica and vermiculite appear to control K‐selectivity in the low K‐saturation range common in certain montmorillonitic soils.
Soil Water Depletion by A Hardwood Forest in Southwestern Wisconsin
Authors: Sartz Richard S.
Published: July 2010

Soil water depletion by cut and uncut forest on a north slope was measured for 3 years with a neutron meter. Depletion by the uncut forest began early in the growing season at all depths measured and continued at a nearly constant rate until leaf fall. Seasonal depletion in a 1.5 m soil mantle averaged 188 mm on uncut plots, 87 mm on clearcut plots, and 57 mm on plots without vegetation. The amount of depletion increased with mantle depth; thus cutting had a greater water‐saving effect on deeper soils. Estimates of evapotranspiration by uncut forest agreed closely with empirical estimates of potential evapotranspiration.
Visual Recorder for Energize‐Deenergize Cycles
Authors: Benz L. C. , Doering E. J. , Dubuque D. E.
Published: July 2010

An inexpensive modification for an FW‐1 water stage recorder to provide a record of energize‐deenergize cycles is described. The system can be used in any equipment or process operation and provides a visual record of the performance.
Production of Permanganate Ion by Sodium Hypochlorite Treatment to Remove Soil Organic Matter
Authors: Anderson J. U. , O'Connor G. A.
Published: July 2010

The pink color characteristically produced during NaOCl treatment of soil to destroy organic matter was studied. Colored extracts were analyzed for Mn content and Redox potential. A spectrophotometer scan of one extract was compared with a scan of KMnO4 solution, and the extract color was shown to be caused by the MnO4‐ ion. The time of appearance and the intensity of the color were related to the organic matter contents of the samples. The source of the Mn was probably Mn(II) released from organic matter during oxidation. The MnO4‐ color appeared when the Redox potential shifted to about + 1.2 V, and was thus a reliable indicator of the approximate end of the organic matter oxidation process.
Ferruginous Concretions in a Poorly Drained Soil of Alberta
Authors: Pawluk S. , Dumanski J.
Published: July 2010

Investigations into the nature of a poorly‐drained soil pedon developed from acid shales in the Peace River region of Alberta, Canada, revealed the presence of ferruginous concretions in the A and B horizons. Concretions from both horizons were separated into two groups, magnetic and nonmagnetic. Magnetic properties were attributed to the preesnce of maghemite. This mineral was associated with iron oxides amorphous to X‐rays in the A horizon and with hematite in the B horizon. Iron oxide in nonmagnetic concretions from the A horizon was X‐ray amorphous while that in the B was crystallized as both goethite and hematite.

Magnetic concretions from the A horizon showed dense areas when viewed in thin‐sections and contained less organic matter and oxalate extractable iron than the associated nonmagnetic concretions.

An authigenic origin is suggested for the concretions.
Dynamic Measurement of Soil and Leaf Water Potential With a Double Loop Peltier Type Thermocouple Psychrometer
Authors: Chow T. L. , de Vries J.
Published: July 2010

Details on the construction, calibration, and performance of a three‐terminal double loop thermocouple psychrometer are given. (This psychrometer design was originally conceived and constructed by Dr. W. H. Gardner, Dep. of Agronomy, Washington State University, Pullman, Wash., USA). The thermal stability of this psychrometer is about 40 times better than that of the two‐terminal psychrometer (Spanner type) for ambient temperature fluctuations with a time rate of change greater than 0.2C/min. The response behavior of a fritted glass bulb and a ceramic bulb psychrometer was tested for vapor and for liquid phase water movement. For vapor phase flow the fritted glass bulb exhibited a shorter response time than the ceramic bulb psychrometer, whereas the reverse was true when water movement was predominantly in the liquid phase. Water potential measurements carried out on silty clay and silt loam soil samples were within ±0.4 bar of the porous plate extractor equilibrium values. A system that facilitates automatic and continuous in situ measurement of soil water potential using the three‐terminal psychrometer is described.
The Effect of Saturating Cations on the Adsorption of Dasanit®, O,O‐diethyl O‐[p‐(methyl sulfinyl) phenyl] phosphorothioate, by Montmorillonite Suspensions
Authors: Bowman Bruce T.
Published: July 2010

A study was conducted to examine the adsorptive behavior of Dasanit in montmorillonite suspensions as affected by saturating cations and the clay suspension concentration. Adsorption isotherms, similar to Type III or Class “S” isotherms, were constructed for 10 cation‐saturated montmorillonites. Infrared spectroscopy was used to examine the relative polarities of the sulfoxide, sulfone, phosphoryl, and carbonyl groups as they occur in Dasanit, in some of its oxidation products, and in several other insecticides. Despite its polar nature, Dasanit did not appear to adsorb on the interlayer surfaces of montmorillonite. X‐ray diffraction data for dry Dasanit‐montmorillonite systems showed a maximum interlayer expansion of 2.7Å. Kinetic data showed that the adsorption process reached equilibrium in less than 15 min. The sequence of the upper linear segments of the 10 isotherms appeared to be related to valence, atomic weight, and co‐ordinating habits of the saturating cations. The Fe‐montmorillonite system adsorbed the most Dasanit. At a suspension concentration of 15 mg/ml, this system removed 99% of the Dasanit from solution. The maximum adsorption value obtained for Fe‐montmorillonite was 0.354 mg/mg clay at a suspension concentration of 0.25 mg/ml. This value corresponded to approximately 4.8 Dasanit monolayers on the exterior clay surface. Desorption studies indicated that those clays with the greatest adsorption capacity exhibited the least desorption tendency. The decreasing order of desorption was Na − > Ca − > Al − > Cu − montmorillonite.
Effects of Straw, Calcium Chloride, and Submergence on a Sodic Soil
Authors: Puttaswamygowda B. S. , Pratt P. F.
Published: July 2010

The effects of straw and CaCl2 during 130 days of submergence, and the effects of these amendments under submerged aerobic vs. anaerobic conditions for a period of 30 days were studied. Comparisons of pH, EC, Na, Ca + Mg, K, Fe, the optical density of the water extract, and ESP were used to evaluate the effects of these amendments. The straw and straw + CaCl2 treatments had the largest effect in lowering the pH and the ESP, increasing the Na and Ca + Mg concentrations and the EC. Submerged anaerobic conditions had the largest effect on promoting these reactions. The concentration of Fe2+ was highest in the straw treatments whereas CaCl2 had a depressing effect on the soluble Fe2+. The optical density was lowest in the straw plus CaCl2 amendment treated soil and the effect of this treatment was larger under anaerobic conditions.

Wheat straw under anaerobic conditions caused an increase in the sum of Na plus Ca plus Mg that was about three times greater than the sum of these cations in the straw itself. In combination with CaCl2 wheat straw reduced the loss of Ca from solution observed when CaCl2 alone was added to soil.
Hydrolysis and Availability of Pyrophosphate in Tropical Soils
Authors: Juo A. S. R. , Maduakor H. O.
Published: July 2010

Hydrolysis and retention of pyrophosphate were studied in selected Nigerian soils. Hydrolysis proceeded readily in the surface soils with half‐lives ranging from 4 to 14 days. Rate of hydrolysis was much slower in the subsoils when compared with their corresponding surface soils. The pyrophosphate halflives in these subsoil samples ranged from 16 to more than 64 days. It was also found that the subsoil samples retained more pyrophosphate resistant to hydrolysis than associated surface soil.

Soils retained greater amounts of pyrophosphate than orthophosphate against 1N NH4Cl extraction although the relative amounts retained by the soils studied followed the same trend.

A short‐term P uptake experiment showed that pyrophosphate could be considered as equally effective as orthophosphate as sources of P for plants.
Cotton Root Growth and Uptake of Nutrients: Relation of Phosphorus Uptake to Quantity, Intensity, and Buffering Capacity
Authors: Khasawneh F. E. , Copeland Jane P.
Published: July 2010

Cotton (Gossypium hirsutum var. ‘Stoneville 213’) was grown in greenhouse pots containing Hartsells fine sandy loam. Four rates of P were employed and the crop was harvested on three different dates. Dry matter yield of tops and uptake of P were measured. Roots were recovered and their length determined. These data were used to calculate a rate of P uptake per meter of roots which in turn was related to quantity and intensity of soil P. A parameter that combines the effects of quantity, intensity, and P buffering capacity was derived, and rate of P uptake was found to be related to this parameter. Rate of P uptake increased with rate of root growth.
A Method of Statistically Interpreting Soil Data for Agricultural and Engineering Land Use
Authors: Kloosterman B. , Lavkulich L. M.
Published: July 2010

A methodology (model) was developed by which soils can be rated, inputs to improve the soil can be determined, and estimates of input costs can be calcuated. Routine soil survey data was used to make interpretations and to illustrate the characteristics of the methodology. Interpretations, including cost estimates, were made for suitability for cash cropping and suitability for roadbed construction. The quantitative soil interpretations were made by statistical procedures notably factor analysis, correlation and regression analysis. Various methods of using soil pedon data were compared and the methodology was evaluated with respect to assumptions and limitations. Recognized soils of the Lower Fraser Valley were quantitatively rated by comparison to the models constructed and hypothetical treatment costs to improve the soils were calculated. The methodology should allow the evaluation of the physical quality of a soil in terms of benefit/cost considerations among alternate land uses.
Analysis of Multidimensional Leaching
Authors: Peck A. J.
Published: July 2010

A simplified analysis is reported of solute leaching from the soil surface to tile drains while infiltration is steady and uniform. Leachate concentration is predicted to decay exponentially with characteristics determined by physical parameters of the system. Predicted decay characteristics are in good agreement with Mulqueen and Kirkham's experimental data.
Steady‐State Seepage in a Hillside
Authors: Morin G. C. A. , Warrick A. W.
Published: July 2010

The complex potential function is obtained for two‐dimensional seepage of water through a hillside using conformal transformations. Two cases are considered: In the first a straight slope of finite length intersects an infinitely wide horizontal plane; in the second, a horizontal plane of finite width is between two symmetric hillsides. Flow nets and graphical relations characterize the flow patterns.
The Persistence of 2,4,5‐T in Greenhouse Lysimeter Studies
Authors: O'Connor G. A. , Wierenga P. J.
Published: July 2010

The persistence of 2,4,5‐T was evaluated in an agricultural soil under favorable microbial conditions in lysimeters. Degradation was most rapid in a soil previously treated with the herbicide if extended periods of time did not separate herbicide additions. The degradation of 2,4,5‐T was more rapid when the herbicide was applied at 40 ppm than when it was applied at 80 ppm. The time required for biological detoxification varied from 43 to 85 days depending upon pretreatment and concentration of the applied herbicide.
Foliar Chloride Levels in Some Eastern Australian Plantation Forests
Authors: Turner J. , Kelly J.
Published: July 2010

Variation in foliar chloride concentrations in New South Wales, Australia, plantation forests were investigated as part of the forest tree nutrition program. Mean foliar chloride concentration was found to decrease with increasing distance from the Pacific Ocean (up to 82% variation accounted for depending on species) and to increase with increasing rainfall and/or number of wet days in the 12 months, covering the growing season, prior to sampling (up to 85% of variation accounted for). Consistencies between species differences were found in foliar chloride concentration. For example at a given location, Eucalyptus pilularis was always higher than both Pinus radiata and Pinus elliottii.
Soil Concretions: II. Mineralogical Analysis
Authors: Gallaher R. N. , Perkins H. F. , Tan K. H. , Radcliffe D.
Published: July 2010

Mineralogy of soil concretions, collected from Henry, Iredell, Tifton, and Decatur soils of the southeastern USA, were studied by DTA, X‐ray diffraction, and electron microprobe analysis. The results indicated the presence of considerable differences in mineralogical composition of concretions formed under different conditions. Although they were basically composed of 1:1 and 2:1 lattice type of clay minerals, quartz, and feldspars, Iredell soil concretions appeared to contain in addition appreciable amounts of amphibole and goethite compared to concretions of Henry soil. On the other hand Tifton soil concretions were made up of predominantly quartz, some 1:1 lattice type of clay mineral, and sesquioxides including gibbsite and hematite. Concretions from Decatur soil appeared to consist partly of amorphous minerals in addition to material, which exhibited X‐ray diffractions characteristic of the mineral psilomelane. It was concluded that Fe‐Mn concretions from Henry and Iredell soils had more complex mineralogy than those found in Tifton and Decatur soils. Mineralogy of Fe‐Mn concretions of Henry and Iredell soils also revealed less intense soil weathering than was indicated by concretions in Tifton soil that contained plinthite.
A Digital Programmer for the Heinrich Miniature Probe Attachment for an X‐Ray Emission Spectrograph
Authors: Barnhisel R. I. , Stapp I. P.
Published: July 2010

A solid‐state digital programmer was developed to drive a Heinrich miniature probe attachment for an X‐ray emission spectrograph. This allowed the automated operation of the X‐ray emission spectrograph during analysis of transects in a variety of studies such as: clay films associated with ionic diffusion, ionic distribution in plant tissue, etc.
Residual Soil Phosphorus Under Sustained Cropping in the Humid Tropics
Authors: Brams E.
Published: July 2010

Residual P in river terrace soils of the West African humid uplands sustained satisfactory yields of Funk G‐901 maize (Zea mays L.), Anethoda rice (Oryza sativa L.), and Mares groundnut (Arachis hypogaea) under a sequence of continuous cropping for 3 consecutive years. Up to 90 kg/ha soluble P applied at the inception of the cropping sequence failed to elicit a yield increase when other cultural parameters were maintained at levels recommended as adequate for satisfactory yields under these conditions.

At the start of the experiment the soil had already attained a residual P level of 55 kg/ha, the Ca + Mg concentration averaged 0.5 meq/100 g soil, and fresh crop and cover residues contributed 18 metric tons/ha of organic matter to the 15‐cm soil depth each year.

Lime applied in the last year raised soil pH from 4.8 to 5.1, reduced Al base‐saturation from 30% to 9%, and probably contributed to the increase in groundnut yield, although this effect was not experimentally tested. In the 3rd year a second application of the P treatments after liming did not induce a significant increase in yield over the check (0‐P) or in those plots which had received only the P treatment initially.

In soils where exchangeable Al comprised 30% or less of the base saturation, the conversion of soluble P into insoluble Al and Fe phosphates apparently was not a yield‐limiting reaction. Phosphorus fixation, particularly as Al phosphates, is a recalcitrant problem for soils in the humid tropics, but this is not true for soils under sustained cropping. By using the same crop varieties and soils similar to those used in this study, subsistence farmers could intensify their operations on selected sites utilizing residual P for extended periods without soil P becoming a yield‐limiting factor.
Effect of Exchangeable Cations on Lateral Movement of Sulfate in Excised Roots
Authors: Franklin R. E.
Published: July 2010

Autoradiographs of histologic sections from excised corn (Zea mays) roots exposed to 35S labeled SO42‐ after pretreatment with K+, Ca2+, or Al3+ are shown. The autoradiographs indicate that the permeability of the epidermal layer to sulfate is severely restricted when pretreated with K+ but not when pretreated with Ca2+ or Al3+. Apparently this effect is associated with the cation exchange sites located in or near the epidermal layer and results from the electrostatic repulsive forces opposing anions which approach the epidermis, where the negatively charged sites are first encountered. The repulsive force would be an inverse function of the degree neutralization of the exchange sites by adsorbed cations which is in the order Al3+ > Ca2+ > K+.
Slick Spots in Southeastern Nebraska—Patterns and Genesis
Authors: Lewis David T. , Drew James V.
Published: July 2010

Slick spots formed in Peoria loess near the crests of interfluves in southeastern Nebraska were studied in relation to their distribution and genesis. Peoria loess forms a discontinuous mantel over a maturely dissected plain of Kansan till. Soils within the slick spots are low in chroma, contain some soluble salts, and have more extractable sodium than associated soils formed in Peoria loess. Calculations indicate that clay formed per unit of nonclay lost was greater in a slick spot soil profile than in an adjacent soil profile. Subsurface data indicate that the configuration of an erosion surface cut into Kansan till underlying the slick spot and the differential permeability of Illinoian sediments above the till contribute to the occurrence of a perched ephemeral water table in the loess beneath the slick spot. The evidence suggests that soluble products of weathering, including Na and Ca, are added to the slick spot by capillary rise from a perched water table following periods of above average precipitation and accumulate in the slick spot during subsequent periods of intense evapotranspiration.
Effects of Drainage and Organic Amendments on the Reclamation of a Sodic Soil Cropped with Rice
Authors: Puttaswamygowda B. S. , Wallihan E. F. , Pratt P. F.
Published: July 2010

In a greenhouse pot culture study, effects of drainage and organic amendments on the reclamation of a saline sodic soil material under submerged conditions were studied with and without the presence of a rice crop (Oryza sativa L.). In drained soils, application of dairy manure, sugar, straw or straw + CaCl2 increased the rate of drainage and decreased the electric conductivity (EC) and exchangeable sodium percentage (ESP). Without drainage, treatments were less effective. Crop growth hastened the reclamation process by increasing the volume of water drained and the concentration of Ca + Mg in the drainage water.

Drainage had a significant effect on the vegetative growth of rice, percentage of earbearing tillers, and straw and grain yield. In the undrained condition, organic soil amendments, except dairy manure, adversely affected the straw and grain yield.
Characterization of the Forest Floor in Stands along a Moisture Gradient in Southern New Mexico
Authors: Wollum A. G.
Published: July 2010

Forest floor properties of stands along a moisture gradient from dry, represented by a piñon‐juniper stand (Pinus edulis Engelm—Juniperus scopulorum Sarg.), to wet, represented by a white fir stand (Abies concolor [Gordon & Glend.] Lindl.), were studied. Dry weights and amounts of nutrients were directly related to the moisture gradient. For example, dry weights of the forest floor increased from 9.4 to 80.8 metric tons/ha from the dry to the wet end of the moisture gradient, respectively. Nutrient concentrations were not related to the moisture gradient with the exception of K. In the more mesic stands sufficient water appears to have been present to allow substantial leaching of K from the forest floor.
Growth and Wood Properties of Loblolly Pine on a Piedmont Subsoil as Influenced by Early Fertilization
Authors: Van Lear D. H. , Saucier J. R. , Goebel N. B.
Published: July 2010

A field study was conducted on an impoverished “borrow” area in the South Carolina Piedmont to determine the response of loblolly pine (Pinus taeda L.) seedlings to various fertilizer treatments. Treatments were applied for 4 consecutive years to individual seedlings outplanted for 2 years. At the end of the fertilization period, seedlings receiving N, either alone or in combination with P and/or K, were significantly taller than seedlings in other treatments. Ten years after the last fertilizer application, trees treated with N, with or without other nutrients, averaged 0.6–1.6 m taller and 23–30% larger in diameter than control trees. Merchantable tree volume was at least doubled by N application. Phosphorus and potassium, at the rates used, had no effect on growth. Percentage latewood and wood specific gravity were not altered by fertilization.
Spheroidal Halloysite in a Guatemalan Soil
Authors: Askenasy P. E. , Dixon J. B. , McKee T. R.
Published: July 2010

Mineralogical analyses of clays from two Alotenango soil horizons were made by utilizing transmission and scanning electron microscopy, infrared, X‐ray diffraction, and chemical methods. This report of spheroidal halloysite demonstrates the presence of this mineral form in an area of important volcanic ash‐derived soils where it has not been previously identified. The presence of spheroidal halloysite in Central American volcanic soil and its presence in volcanic soils of Hawaii, Japan, and New Zealand indicate its wide geographic occurrence in soils of volcanic origin. Oblate halloysite spheroids tend to settle preferentially, offering an end‐view along the axis of some particles and correspondingly, reduced 00l X‐ray reflections from portions of layers not parallel to the plane of the powder mount. Halloysite spheroids appear to be composed of roughly concentric layers with occasional interlayer separations. The interior structure suggests inclusion of amorphous cores and interlayers which appear to be removed by 0.5N NaOH. The exterior layers often retain a shell‐like appearance after NaOH treatment. The apparent association of spheroidal halloysite and allophane interlayers suggests that the crystalline component forms alternately with the amorphous one. The crystalline exterior may protect amorphous interior material from rapid alteration and cause allophane to persist in a soil where minerals representing more advanced stages of weathering have accumulated.
Temperature Regimes and Classification of Some Well‐Drained Alpine Soils in Alaska
Authors: Rieger Samuel
Published: July 2010

Temperatures at a depth of 50 cm were taken in four well‐drained alpine soils of interior and south‐central Alaska over a 3‐year period. The soils of the interior, under a strongly continental climate, have a pergelic temperature regime, but those of coastal mountains under a cool maritime climate do not.
Soil Urease: Paucity in the Presence of the Fairy Ring Fungus Marasmius oreades (Bolt.) Fr.
Authors: Norstadt Fred A. , Frey C. R. , Sigg Harold
Published: July 2010

Turf infection by Marasmius oreades (Bolt.) Fr. produced concentric rings of affected soil or fairy ring phenomena. Urease activity of soil invaded by the fungus ranged from 0.86 to 15.4 mg NH4+‐N/100 g per 3 hours, or about 10 to 40% that in unaffected soil. Normal soil from outside the fairy rings had activity ranging from 8.9 to 36.2 mg NH4+‐N/100 g per 3 hours. Urease activity of soil was determined by distillation of NH4+, radioactivity of 14CO2, and respirometry of CO2. In determining urease activity, the quantity of NH4+‐N produced by hydrolysis of added urea was correlated (r = 0.84) with released 14CO2, but was twice as large. The results from respirometry of CO2 agreed with that from distillation of NH4+‐N. The numbers of microbes and urease activity were correlated for fresh soil with coefficients (r) ranging from 0.62 to 0.77. Extractable NH4+‐N was about 40 times larger in affected than in normal soil, although NO3‐‐N was unchanged. Soil pH was reduced about one unit. Urease activity was restored in affected soil by three successive incubations. The decrease in soil urease caused by the fungus likely was concomitant with humus destruction.
Leaching Requirement Studies: Sensitivity of Alfalfa to Salinity of Irrigation and Drainage Waters
Authors: Bernstein Leon , Francois L. E.
Published: July 2010

Alfalfa (Medicago sativa L. cv. Sonora) was grown in 0.6 by 1.5 m greenhouse lysimeters and irrigated with two waters of EC 1 and 2 mmho/cm prepared by adding equivalent amounts of NaCl and CaCl2 to a 0.4 mmho/cm tap water. Yields showed relatively little effect of leaching fraction (LF) within the limits consistent with steady‐state salt balance for suction‐drained lysimeters but decreased 26% at the lowest LF for gravity‐drained lysimeters. Yields with the 2 mmho/cm irrigation water treatments were consistently about 10% less than those with the 1 mmho/cm water. Cessation of leaching or reduction of LF to levels requiring drainage water salinities for salt balance at steady state to exceed 35 mmho/cm, the maximum salinity achievable by alfalfa roots, eventually reduced yields. Yields were significantly higher (by 9%) when leaching was done every third or sixth irrigation than in every irrigation while maintaining the same average LF of 1/32 and 1/16 for the 1 and 2 mmho/cm irrigation waters, respectively. Since alfalfa yield was affected as much by a 1 mmho/cm difference in salinity of the irrigation water as by a ca. 20 mmho/cm difference in salinity of the drainage water, alfalfa yields obviously were not responding to the soil water salinity averaged by depth. Yield response appears to be related rather to the calculated mean salinity against which water was absorbed, which is influenced more by the salinity of the irrigation water than by the salinity of the drainage water.

Steady‐state salinity profiles were achieved after 4 to 8 irrigations when LF was equal to or greater than 1/8, but at lower LF's of 1/16 and 1/32, steady‐state profiles were achieved only after 20 and 55 irrigations, or 1 and 2 years, respectively. Increasing the degree of water depletion caused major salt accumulation at lower depths corresponding to the increased depths at which major water depletion occurred. LF in the broad range that permitted nearly maximum growth had essentially no effect on water requirement (grams water evapotranspired per gram dry matter produced) or on Na and Cl contents of the harvested alfalfa. Increasing irrigation water salinity in the range 0.4 to 2 mmho/cm consistently increased plant Na and Cl contents, but had no effect on water requirement.

Implications of the demonstrated lower leaching requirements for irrigation management and drainage and for water quality assessment are discussed.
An Evaluation of Kinetic and Equilibrium Equations for the Prediction of Pesticide Movement Through Porous Media
Authors: van Genuchten M. Th. , Davidson J. M. , Wierenga P. J.
Published: July 2010

Miscible displacement techniques were used to study the movement of picloram (4‐amino‐3,5,6‐trichloropicolinic acid) through a water‐saturated Norge loam soil. The equilibrium adsorption and desorption isotherms for picloram and Norge loam soil were not single‐valued relations. Picloram mobility was reduced significantly when the average pore‐water velocity was decreased from 145 to 14.2 cm/day. Observed and predicted effluent concentration distributions were compared. Predictions were made with a S/360 CSMP simulation model, using two kinetic rate equations and an equilibrium Freundlich equation. The two kinetic models and the equilibrium model each satisfactorily described the observed effluent concentration distributions at low pore‐water velocities provided the nonsingle‐valued character of the adsorption‐desorption process was included in the calculations. At high pore‐water velocities, the kinetic adsorption models were found inadequate to predict the picloram movement. An empirical model was then developed, based on the assumption that equilibrium existed during displacement and that only a fraction of the soil participated in the adsorption process. This fraction was found to be a function of the average pore‐water velocity. With the empirical model, a reasonable fit between data and calculated effluent curves was obtained for all pore‐water velocities.
Nitrate Adsorption by Some Volcanic‐ash Soils of Southern Chile
Authors: Schalscha E. B. , Pratt P. F. , Domecq T. C.
Published: July 2010

Nitrate adsorption by several soils was determined as the difference between the NO3‐ added and that remaining in the supernatant liquid. A nitrate ion electrode method, which was checked against a phenoldisulfonic method, was used to determine the NO3‐ remaining in the supernatant liquid.

The time required for equilibrations was 16 hours. The amount of NO3‐ adsorbed varied from 1.2 to 7.5 meq/100 g of soil from a 0.05M NO3‐ solution for soils of pH values ranging from 5.3 to 6.1. The amount adsorbed increased with decreasing pH.
Nitric Oxide Sorption by Calcareous Soils: II. Effect of Moisture on Capacity, Rate, and Sorption Products
Authors: Miyamoto S. , Prather R. J. , Bohn H. L.
Published: July 2010

At room temperature, the nitric oxide (NO) sorption capacity of calcareous soils increased with the presence of moisture in an air + NO stream (1.5% NO by volume) and/or in the soils. The largest increase, up to 10‐fold or approximately to the acid‐titratable basicity of soils, occurred when NO and H2O were sorbed simultaneously by initially dry soils from a moist air (humidity > 95%) + NO stream. The sorption rates were proportional to the unused portion of the capacity with the rate constants ranging from 0.02 to 0.03 min‐1 for NO and 0.01 to 0.015 min‐1 for H2O under simultaneous sorption. Initially moist soils sorbed NO from a dry air (humidity < 5%) + NO stream until the soils dried. The rate of NO sorption slowed at initial soil water suctions less than approximately 1 bar. Sorbed NO was recovered as nitrate and reacted with the basicity in moist soils. Less than 20% of the sorbed nitrogen was lost upon heating at 105C for 24 hours.
The Surface Catalyzed Hydrolysis of Parathion on Kaolinite
Authors: Saltzman Sarina , Yaron Bruno , Mingelgrin Uri
Published: July 2010

The decomposition of parathion on various monoionic kaolinites was investigated. The degradation was found to proceed via the hydrolysis of the phosphate ester to p‐nitrophenol and diethyl thiophosphate. The kaolinites were found to catalyze the hydrolysis. The nature of the exchangeable cation greatly affected the rate of hydrolysis. Ca‐kaolinite was the most active in inducing the degradation of parathion, the hydrolysis being twice as fast as in a water solution at pH 8.5 at the same temperature. The presence of a large excess of water decreased the catalytic effect of the kaolinite. The mechanism of the hydrolysis is via adsorption of the parathion upon the exchangeable cation or its hydration shell. The temperature dependence of the process is consistent with this proposed mechanism. The significant catalytic activity of kaolinites and its dependence on the exchangeable cation is important to the understanding of the degradation of parathion in soil and may be utilized in the formulation of parathion for various purposes.
Humods in Relation to Volcanic Ash In Southern Alaska
Authors: Rieger Samuel
Published: July 2010

Analyses of Spodosols in southern Alaska indicate that Humods—well‐drained Spodosols in which the free iron‐carbon ratio in at least part of the spodic horizon is less than 0.2—apparently form only in ashy materials, though not all Spodosols developed in volcanic ash are Humods. Spodosols formed in other materials may have similar morphological properties, but all have narrower ratios and are classified as Orthods. The distribution of the two groups of soils in this cool, humid area is apparently not dependent on differences in precipitation rates, temperatures, or vegetative cover. Wider Fe/C ratios in the ashy Spodosols result from lower concentrations of free Fe rather than from larger accumulations of illuvial C in the spodic horizon. A possible reason for the affinity between low‐iron Spodosols and ashy parent materials is a more ready availability of aluminum from volcanic ash as opposed to the more rapid release by weathering of iron in other materials.
Accretion and Dilution of Nutrients in Young Corn, as Affected by Yield Response to Nitrogen, Phosphorus, and Potassium
Authors: Terman G. L. , Allen S. E.
Published: July 2010

Hybrid corn (Zea mays L.) was grown in infertile soil fertilized with none and three nonzero rates of N, P, or K in separate treatment series; other nutrients were applied in each series at uniform levels. Near‐linear increases in uptake of N, P, or K with amount applied occurred during 25, 41, and 53 days' growth. Concentrations of N, P, or K increased with amount applied and decreased with continued growth in each series; uniformly applied P and K, N and K, or N and P were diluted with increase in dry matter resulting from continued growth and yield response to increasing amounts of the third nutrient. Yield‐concentration relationships in the N response series were similar for N, Ca, Mg, Mn, and Zn. Response to P or K resulted in dilution of all other nutrients. Concentrations of total cations increased with concentrations of N in each response series; the reverse was true with P and K. Thus, the results suggest that a positive relationship between dry matter yields and total cations (C), total inorganic anions (A), and C‐A depends on whether yield response is due to N or to other growth‐limiting factors.
Lime Induced Plant Growth Depression in an Alluvial Entisol from Costa Rica
Authors: Velez J. , Zantua M. I. , Blue W. G.
Published: July 2010

Poor plant growth in field experiments following clearing of a forested virgin Entisol in eastern Costa Rica and the subsequent detrimental effect of lime on growth of warm‐season grasses were studied in greenhouse and laboratory experiments. Greenhouse experiments were carried out with pangolagrass (Digitaria decumbens Stent) by sterilizing a virgin surface soil, limed with 0, 4, and 8 meq/100 g of CaCO3, with heat and gamma radiation. Incubation experiments in the laboratory were conducted with a differentially limed surface soil that had been in pasture for 8 years and its subsoil. Every 2 weeks, for 10 weeks, samples from the incubating soils were extracted with water. Calcium, Mg, K, Na, NO3, SO4, P, and Cl were determined in the water extracts. Electrical conductivity in the soil was measured before and after water extractions. After 10 weeks of incubation, electrical conductivity was measured in saturated soil extracts. Soil organic matter was determined before and after incubation.

The negative effect of lime persisted in the sterilized soils; however, water leaching of unlimed and limed virgin soils markedly improved pangolagrass growth. Laboratory studies showed considerable increases in water‐extractable Ca, NO3, and SO4 ions with increasing lime rates and incubation time in the pasture surface soil and its subsoil. Electrolytes reached a maximum at 2 weeks of incubation. Conductivity measurements higher than 4 mmhos/cm in saturated soil extracts after 10 weeks of incubation indicated harmful concentrations of electrolytes which were apparently derived from lime and biological decomposition of soil organic matter.
Water and Nitrogen Economy of Rainfed Rice as Affected by Soil Puddling
Authors: De Datta S. K. , Kerim M. S. A. A. A.
Published: July 2010

In a field experiment conducted to study the water and nitrogen economy of rainfed rice (Oryza sativa L. variety, ‘Tongil’) grown on montmorillonitic clay, much more water was lost from nonpuddled soil than from puddled soil. In rainfed treatments, the crop suffered from moisture stress for 2 weeks during panicle development. During this time soil moisture tension 10 cm deep was 70 centibars in nonpuddled soil compared with 25 centibars in puddled soil. Water‐use efficiency was calculated by dividing the grain yield values by the amount of water received from rain or applied through irrigation. Water‐use efficiency of rice in the irrigated controls, was 2.5 times higher in the puddled soil than in the nonpuddled soil.

Ammonium and nitrate nitrogen in the soil and plant nitrogen were determined periodically. The large losses of water from nonpuddled soil caused greater nitrogen losses and less nitrogen uptake by rice at all stages of growth. As a result, grain yields of rice grown on nonpuddled soil were significantly lower than yields of rice grown on puddled soil, with or without nitrogen.
Response by Flooded Rice to Phosphate Rocks Varying in Citrate Solubility
Authors: Engelstad O. P. , Jugsujinda Aroon , De Datta S. K.
Published: July 2010

Studies were conducted in the greenhouse and in the field to evaluate several phosphate rocks for flooded rice (Oryza sativa L.). A close relationship was found to exist between first‐crop yield response to applied P and citrate solubility in a series of phosphate rocks representing the theoretical range in this parameter. Greenhouse (TVA) and field data (Thailand) showed quite similar results in this respect.

The same general pattern of effectiveness among sources persisted through the second crop as found for the first crop. The residual effectiveness of triple superphosphate (TSP) remained higher than that of the phosphate rocks; however, the relationship between initial citrate solubility of the phosphate rocks and relative effectiveness in the second crop was rather poor.

A procedure is presented which enables one to make the choice of P source on the basis of both agronomic effectiveness and prices of P in TSP vs. phosphate rock.
Artificial Weathering of Oxidized Biotite: IV. The Inhibitory Effect of Potassium on Dissolution Rate
Authors: Gilkes R. J. , Young R. C.
Published: July 2010

Rates of dissolution of oxidized biotites in 0.1M 0.01M HCl are severely depressed in the presence of 1M KCl. The amounts of Al, Mg, Mn dissolved in the first extraction are similar to those found without KCl, however, subsequent extractions remove these elements at 10–20% of the corresponding HCl rates. This effect may be due to a decreased rate of vermiculite formation, thereby reducing the effective basal area exposed to attack. A decrease in dissolution rate with increasing ferric iron content was still apparent in the presence of 1M KCl.
Effect of Gypsum, Soil Disturbance and Tile Spacing on the Amelioration of Huey Silt Loam, a Natric Soil in Illinois
Authors: Sharma A. K. , Fehrenbacher J. B. , Jones B. A.
Published: July 2010

Gypsum is by far the most commonly used amendment for ameliorating natric or solonetzic soils. Previous laboratory leaching studies with these soils in Illinois indicated that gypsum was more effective on disturbed than on undisturbed soil columns of natric horizons. The present investigation, therefore, was undertaken to formulate an effective field procedure for ameliorating the natric soils in Illinois. Effects of the treatment combinations of 0, 24, and 62 tons/ha of gypsum mixed to 15 or 90 cm or chiseled to 60 cm in soil on plots not tiled or having tile spacings of 3, 9, or 18 m, were studied on Huey silt loam, a natric soil at Newton in south‐central Illinois in terms of corn yields (Zea mays L.), removal of extractable sodium from the soil, corn root growth and development, and water table fluctuations. Corn yields from 1964 to 1971 inclusive and removal of extractable Na from 1964 to 1972 inclusive were studied on all plots. Corn root growth and development studies in 1972 included four 9 m tiled plots with various gypsum and soil disturbance combinations. Water table fluctuations were studied from 1969 to 1972 inclusive on three plots with different treatment combinations.

Of all the combinations studied, 62 tons/ha of gypsum mixed to 90 cm and tiled 3, 9, or 18 m, were the only effective combinations in improving corn yields, removing Na from the soil, and increasing water transmission in the soil. On plots with gypsum mixed to 15 cm only, tiling was not effective, but on plots with gypsum mixed to 90 cm, 3 m tile spacing was significantly better than 18 m spacing in increasing corn yields and improving soil conditions. Mixing the soil to 90 cm without gypsum resulted in reduced corn yields and no improvement in Na removal in comparison to the conventionally treated plots without gysum.
Powdered Metal Plates for Constructing Unsaturated Flow Cells
Authors: Bianchi William C.
Published: July 2010

Described is the theoretical design, construction and observed characteristics of sintered stainless steel powdered metal plates which could be used in control sections of an unsaturated flow cell (J. W. Cary, 1968, Soil Sci. Soc. Amer. Proc. 32:3–5).
Scanning Electron Microscopy as Applied to Organo‐Mineral Complexes in Alkaline Extracts of Soil
Authors: Dormaar J. F.
Published: July 2010

Lyophilized alkaline extracts from a Black Chernozem (Udic Haploboroll) Ah horizon were scanned in a scanning electron microscope. The micrographs obtained show the physical associations of organic and mineral matter before and after acidification and purification. A large percentage of the organoclay mineral complexes present in humic acids is probably formed during acidification.
Electrochemistry of Sodium‐Montmorillonite Suspensions: I. Chemical Stability of Montmorillonite
Authors: Shainberg I. , Low P. F. , Kafkafi U.
Published: July 2010

The chemical stability of four Na‐saturated montmorillonites differing in their isomorphous substitution was studied by following the change of specific conductance, Na+ activity and pH of their aqueous suspensions at several clay concentrations. It was found that the change in specific conductance is proportional to the square root of time and that the proportionality constant is linearly related to the degree of octahedral substitution. Further, a linear relation exists between the change in specific conductance and the change in Na+ activity. A hypothesis to explain these observations is presented.
Virulence of the Alnus Endophyte after In Vitro Cultivation
Authors: Rogers R. D. , Wollum A. G.
Published: July 2010

A technique has been devised for maintaining the virulence of the endophyte of Alnus glutinosa L. during in vitro cultivation. Essential to the technique are the inclusion of an ether extract of Alnus roots and cycloheximide and chloramphenicol to the artificial medium. Using the devised medium, endophyte virulence has been maintained for 14 days whereas in the absence of the ether extract and antibiotics, virulence was lost within 3 days. Nodules that are subsequently formed after inoculation of plants with the incubated endophyte are normal. Visible nodules were formed within 7 to 12 weeks after inoculation, a period which was comparable to the nodulation time of control plants inoculated with fresh crushed nodules. In addition, the nodules were capable of reducing acetylene which is indicative of nitrogen fixing activity. Also, during this study it was found that freeze‐drying nodules does not reduce the virulence of the nodule‐inducing endophyte.