bluuebunny/crossref_metadata_2025 huggingface dataset:
Pore Size Distributions as Measured by the Mercury Intrusion Method and Their Use in Predicting Permeability
Authors: Klock G. O. , Boersma L. , DeBacker L. W.
Published: July 2010

Several equations to predict the permeability of a porous medium from its pore size distribution have been proposed. Pore size distributions of soils are most commonly obtained from soil water release curves. In the present study pore size distributions were obtained by the mercury intrusion method and used in the calculation of intrinsic permeability. The calculated permeability values were compared with measured values for a range of pore size distributions.

Permeabilities and pore size distributions of 54 systematically selected particle size classes of glass beads and sand were measured. Limits of the particle size classes ranged from 44–53 to 208–246 microns for the particle diameters. Millington and Quirk's equation was used to calculate the permeabilities. The calculated permeabilities agree with the measured values only when a correction factor is used. Some limitations of the mercury intrusion technique used to obtain pore size distributions are discussed.
Regularity of Interstratification as Affected by Charge Density in Layer Silicates
Authors: Sawhney B. L.
Published: July 2010

Successively larger sorptions of Cs or K by most Ca‐saturated vermiculites collapsed their alternate layers, producing regularly interstratified mica‐vermiculite layer sequences. Additional sorption then collapsed the expanded layers within the interstratified mineral until the entire sample was collapsed to the mica structure. Sorption of Cs or K by Ca‐saturated montmorillonites, on the other hand, did not collapse their interlayers even when almost half of their exchange sites were occupied by Cs or K. Additional sorption then collapsed some layers producing random, not regular, interstratification.

The ease of collapse of interlayers and the subsequent regularity of interstratification was related to the layer charge density of the mineral. The large charge density in vermiculite collapses the layers readily on Cs or K sorption. The collapse in one layer prevents the entry of these cations in the adjacent layer, producing regularly interstratified mica‐vermiculite layer sequences. The lack of collapse and the random interstratification in montmorillonites, on the other hand, is attributed to their small charge density.
Contribution of Metal‐Organic Complexing Agents to the Transport of Metals to Roots
Authors: Hodgson J. F.
Published: July 2010

The movement of many cations in soils can be influenced by the presence of synthetic chelates and soluble organic matter capable of forming metal‐organic complexes. To understand how these complexes may contribute to the nutrition of plants, a means is needed to interpret their thermodynamic properties and behavior in solution culture experiments in terms of their effect on roots growing in porous media such as soils. For this purpose, a theoretical model is proposed to describe the contribution of complexed species to the flux of nutrients to roots. The model is developed from considerations of diffusion in response to concentration gradients, mass flow of water to a simulated root, and chemical equilibria between complexing agents and competing cations, and is evaluated in terms of different boundary conditions. The model illustrates how metal‐complexing can contribute more to the nutrition of plants grown in a porous medium such as a soil than in nutrient solutions. It also shows how competing ions can have a potentially beneficial effect, as well as the obvious deleterious effect, on the contribution of complexing agents to the nutrition of plants.
Reactions of EDTA Complexes of Fe, Zn, Mn, and Cu with Soils
Authors: Norvell W. A. , Lindsay W. L.
Published: July 2010

The Fe, Zn, Cu, and Mn complexes and the Na salt of EDTA (ethylenediaminetetraacetic acid) were reacted with suspensions of acid, neutral, and calcareous soils. The initial concentration of chelate was 1 × 10‐4M or on a soil weight basis, 11.2, 13.1, 12.7, and 11.0 ppm of Fe, Zn, Cu, and Mn, respectively. Suspensions were aerated and shaken continuously for periods of 2 hours to 30 days. At the termination of each reaction period the pH of the suspensions was measured; following centrifugation, the supernatant solutions were analyzed for Fe, Zn, Cu, Mn, Ca, and Mg by atomic absorption spectrophotometry. The concentration of 14C‐labeled EDTA was determined by liquid scintillation.

FeEDTA was stable in soil suspensions of pH 5.7 and 6.1, moderately stable at pH 6.75, and unstable at pH 7.3 and 7.85. This behavior was satisfactorily predicted using formation constants to describe equilibria of EDTA with Fe3+, Ca2+, and H+, with the assumption that the Fe3+ concentration was controlled by the solubility of amorphous iron(III) oxides. ZnEDTA and CuEDTA were most stable in suspensions near neutrality. In acid soils Cu and Zn were increasingly displaced by Fe as pH decreased while in calcareous soils these metals were displaced by Ca as pH increased. The loss of Mn from MnEDTA was very rapid in all soils and was essentially complete in less than one day from suspensions of pH 6.1 to 7.85.
Design and Performance of an Osmotic Tensiometer for Measuring Capillary Potential
Authors: Peck A. J. , Rabbidge R. M.
Published: July 2010

An osmotic tensiometer makes use of a confined aqueous solution, instead of pure free water, as the reference state in measuring soil‐water potentials. The membrane separating the confined solution from soil water is highly impermeable to the confined solute (polyethylene glycol, molecular weight 20,000), but exchange of much smaller molecules and ions occurs. Thus the capillary potential of soil‐water is measured unless soil solutes are excluded from the instrument by a vapour gap. The advantage of this instrument over conventional tensiometers is that measurements of capillary potential can be made throughout the range 0‐ to −15‐bar. Tests and observations show that osmotic tensiometers can be useful for measurements of capillary potential at depths greater than about 10 cm during the redistribution of soil water, and its uptake by plants. For accurate data, zero checks should be made when possible, and instrument temperature should be recorded to enable correction for its effect on each reading.
Effect of pH on Labile and Soluble Phosphate in Soils
Authors: Murrmann R. P. , Peech Michael
Published: July 2010

A study was made of the effect of varying soil pH, by the addition of either HCl or Ca(OH)2, on the concentration of phosphate in 0.01M CaCl2 extract as well as the amount of labile phosphate, as determined by isotopic exchange, in both acid and limed soils to which liberal amounts of superphosphate had been applied over a long period of time but to which no phosphate had been applied for at least five years prior to sampling.

For any given soil, the amount of labile phosphate in the soil and the concentration of phosphate in soil solution both reached a minimum value at about pH 5.5 and increased rapidly as the pH was increased or decreased from this value. When the value of pH + pH2PO4 was plotted against pH — ½pCa on the conventional calcium phosphate solubility diagram, the experimental points did not fall on the solubility isotherm of any known crystalline phosphate compound except when the pH was increased sufficiently to cause supersaturation with respect to octocalcium phosphate at which point octocalcium phosphate began to precipitate and the values of pH + pH2PO4 fell on the octocalcium phosphate solubility isotherm.

The observed variation in the amount of soluble and labile phosphate with pH was found to be reversible. The addition of soluble phosphate to a soil also resulted in increases in the amounts of soluble and labile phosphate at any given pH. These findings would support the conclusion that the phosphate concentration in soil solution was determined by the amount of labile phosphate rather than by the solubility of some crystalline phosphate as the pH of the soil varied.
Environmental Factors Influencing the Sorption of Atmospheric Ammonia by Soils
Authors: Hanawalt Ronald B.
Published: July 2010

Under conditions of controlled temperature and atmospheric ammonia concentration, the sorption rate for atmospheric ammonia by six soils from New Jersey decreased only slightly over exposure periods up to 4 days and averaged 55 to 74 kg of NH3‐N/ha/year. The ammonia sorption rate for these soils increased rapidly with increasing ammonia concentration and moderately with increasing temperature. Calculated energies of activation suggest that sorbed ammonia is held by chemical bonds rather than by physical adsorption. Increasing the velocity of gas flow across the soil surface brings more ammonia into contact with the soil and thus enhances the sorption rate. Soils sorb significant amounts of ammonia from the atmosphere which under some environmental conditions may constitute a major mechanism in the transfer of nitrogen form the atmosphere to soils.
The Formation of Nitrate from Ammonium Nitrogen in Soils: IV. Use of the Delay and Maximum Rate Phases for Making Quantitative Predictions
Authors: Sabey B. R. , Frederick L. R. , Bartholomew W. V.
Published: July 2010

Estimation of the amount of nitrate accumulation occurring in soil requires an understanding of the delay period and maximum rate of nitrate accumulation under defined environmental conditions. The actual maximum rates and delay periods of nitrate accumulation varied greatly between soils at several constant temperatures, whereas the relative maximum rates and delay periods were more nearly constant at any one temperature.

An equation for estimating nitrate accumulation, which includes maximum rate and delay indexes, is suggested. Temperature‐rate and temperature‐delay indexes are presented for several soils. Values for different temperatures were predicted from actual values determined at only one temperature. The concept of delay periods and maximum rates should help evaluate the influence of other factors on nitrate accumulation.
Interdependence of Water Drop Energy and Clod Size on Infiltration and Clod Stability
Authors: Moldenhauer W. C. , Kemper W. D.
Published: July 2010

The decline of intake rates as successive increments of water drop energy were applied to various sizes of soil fragments of two Iowa and two Colorado soil types is presented. There was a wide spread between intake rate of the 8‐ to 20‐mm size range and those of all other sizes after the first increment (1.25 cm as 5‐mm drops) was applied. The intake rate of the 8‐ to 20‐mm size declined rapidly after the first or second increment. Final intake rates were not correlated with aggregate stability in this study. There was a negative correlation between clay content and final intake rates. Final intake rates after disintegration of large soil fragments in many cases were lower than when initial size ranges were small.
Proton Transfer Reactions at Clay Mineral Surfaces
Authors: Raman K. V. , Mortland M. M.
Published: July 2010

The transfer of protons from a protonated species to an uncharged molecule at the surface of clay minerals is an important process. NH+4, pyridinium, ethylammonium, methylammonium, and protonated‐urea montmorillonite and nontronite complexes were equilibrated over NH4OH, pyridine, methylamine, or with 3‐aminotriazole, and the status of the adsorbed molecule determined using infrared spectroscopy. Proton transfer or retention by a species depends on two factors: (i) the relative basicities of the two interacting compounds and (ii) the relative concentration or activities of the reactants and products. Indications were that the clay mineral altered the basicity of some compounds compared to the others. The relative order of basicity of the compounds studied here were found to be 3‐aminotriazole > ammonia > methylamine = ethyamine > pyridine > urea. Such proton transfer reactions as have been demonstrated here to occur in model clay‐organic complexes are undoubtedly processes of importance in natural systems.
pH‐Dependent Bonding of Potassium by a Spodosol
Authors: Bartlett R. J. , McIntosh J. L.
Published: July 2010

A Spodosol Ap high in extractable Al and pH‐dependent CEC was limed to pH 6.3, producing deficiency of K in tomato seedlings. This was evidenced by lowered plant yields and concentrations of K in the tissue, compared with plants grown in acid samples of the soil. Soil chemical studies were undertaken to further examine the magnitude and mechanism of this phenomenon. Treatment of acid soil samples with increasing levels of CaCO3, CaSiO3, CaHPO4, or CaF2 markedly raised CEC along with pH and lowered activity of K and extractable Al.

It was hypothesized that hydroxyl, phosphate, or fluoride ions neutralized positive charges on Al. This freed negatively charged exchange sites, and thereby raised CEC. With increased CEC, the percentage saturation of the exchange complex with K (and, therefore, availability of K) was decreased, compared with the untreated soil.
Variation of Soil Properties within Mapping Units of Soils with Contrasting Substrata in Northwestern Ohio
Authors: McCormack D. E. , Wilding L. P.
Published: July 2010

Variation of soil properties within mapping units of Seward, Rimer, Wauseon, Rawson, Haskins, and Mermill soils in northwestern Ohio was statistically summarized. These series have sandy or loamy upper sola that overlie a fine‐textured substrata. Ten randomly selected profiles within each of 22 delineations of these soils were characterized by field study. Standard deviation, standard error of the mean, and coefficient of variation were computed for each of 48 selected properties. The most variable properties were depth to mottling, depth to fine‐textured discontinuity, horizon thickness, texture, and chroma of the B2t horizon, percent of mottles having chromas of two or less, and grade of structure. Hue, value, and pH of all horizons, texture of the IIB horizon, and size and shape of structure were the least variable. 54% of the profiles had IIB horizons in areas mapped as soils in which this horizon was lacking; 78% had IIB horizons in areas mapped as soils having this horizon. Little difference in other properties was noted between areas mapped as soils representing the two conditions. These soils were correctly classified with regard to soil series at 37% of the 220 observations. Careful study in such complex areas is essential before establishing a legend.
Physical Properties of Peats as Related to Degree of Decomposition
Authors: Boelter D. H.
Published: July 2010

Important physical characteristics, such as water retention, water yield coefficient, and hydraulic conductivity, vary greatly for representative northern Minnesota peat materials. The differences are related to the degree of decomposition, which largely determines the porosity and pore size distribution. Fiber content (> 0.1 mm) and bulk density are properties often measured to indicate the degree of decomposition of peat materials and are criteria used to distinguish fibric, hemic, and sapric peat types.

Regression analyses showed a curvilinear relationship of water contents at saturation, 5 mbar, 0.1 bar, and 15 bar suctions, to fiber content (> 0.1 mm) and bulk density with coefficients of multiple determination (R2) ranging from .66 to .88. Regression analyses of the logarithm of hydraulic conductivity on fiber content (> 0.1 mm) and bulk density indicate a linear relationship (r2 = .54), although not as great due to the variability of hydraulic conductivity.

Thus the classification of peat materials and organic soils based primarily on degree of decomposition as measured by fiber content and bulk density would relate significant information about their physical characteristics.
Primary and Secondary Origin of “Nonextractable” Soil Inorganic Phosphorus
Authors: Syers J. K. , Williams J. D. H. , Tyner E. H. , Walker T. W.
Published: July 2010

“Nonextractable” soil inorganic phosphorus can have both a primary and a secondary origin. Apatite included within other minerals and phosphorus distributed throughout mineral lattices constitute the primary sources. “Nonextractable” secondary phosphorus accumulates during soil development and is associated with hydrated sesquioxides.
Relation between Staudinger Indices and Precipitabilities of Polysaccharides Extracted from Forest Soils
Authors: Saini G. R. , Salonius P. O.
Published: July 2010

Fractional precipitation of polysaccharides extracted with hot water from forest soils indicated that the organic layers contained a mixture of up to three polysaccharide fractions.

The precipitabilities of the polysaccharide fractions ranged between 0.48 and 0.74 and the Staudinger indices had a range of 70 to 150. The precipitabilities and the Staudinger indices were inversely related in a linear fashion.
Radiocarbon Chronology of the Florida Everglades Peat
Authors: McDowell L. L. , Stephens J. C. , Stewart E. H.
Published: July 2010

Radiocarbon measurements on two peat profiles near Belle Glade, Fla., indicate that peat formation in the Upper Everglades began during late Hypsithermal time, about 4,400 years B.P. (before present). Initially, peat development was very slow. About 500 to 1,000 years were required to build up the 7.6 cm of basal mucky peat, composed of a mixture of marl and organic matter. Then about 3,500 to 4,000 years ago, as a result of environmental changes, plant growths increased rapidly and were preserved as fibrous peats with very little mineral admixture. This rapid development of peat is contemporaneous with a rapid eustatic rise in sea level.

Peat development proceeded rapidly (about 7.3 cm/century) from about 3,500 years to 1,200 years B.P. During this interim the existing peat, measuring about 1.37 m in thickness, was developed. By A. D. 1914 the peat had developed to a depth of about 3.65 m. This represents an average peat development of about 8.4 cm/century (4,400 B.P. to A.D. 1914).

The Everglades Basin, prior to the initiation of drainage programs in the early 1900's, was inundated for a large part of the year. Since drainage, over a period of 50 years, about 1.8 m, or one‐half, of the original profile has been destroyed by the prevailing aerobic conditions.
Clay Translocation and Albic Tongue Formation in Two Glossoboralfs of West‐Central Wisconsin
Authors: Ranney Richard W. , Beatty Marvin T.
Published: July 2010

Soil columns from two Typic Glossoboralfs were dissected to separate albic tongues and argillic B horizon material. Tongues and B horizon material have similar coarse/fine (50‐20µ/20‐2µ) silt ratios in the upper B horizon indicating that tongues could have been formed in place by eluviation of clay from certain zones of the B horizon.

Lower in the B horizon the tongues consistently have different coarse/fine silt ratios than does adjacent B horizon material. Mineralogical analysis of silts gave no indication of differential weathering of quartz, alkali feldspars, or mica which together make up 85 to 90% of the fine silt (20‐2µ). The particle‐size distribution of silts in the lower albic tongues is taken to indicate that translocation of silts and sands has been involved in the formation of these tongues.

Higher proportions of quartz, feldspars and mica in the coarse clay (2‐.2µ) of upper albic tongues indicate that montmorillonite, vermiculite, pedogenic chlorite and kaolinite have been preferentially removed. This, and the mineralogical similarity of fine clay (<0.2µ) between eluvial and illuvial zones, indicate that clay translocation in these soils is accomplished primarily by movement of clay particles in suspension without appreciable dissolution of crystal structures.

Spodic horizons have begun to form in the albic horizons of some Glossoboralfs of the study area and Spodosols are common in coarser parent materials. Processes of illuviation inferred from this investigation, however are greatly different from those generally considered typical of Spodosols.
Profile Modification of a Slowly Permeable Soil
Authors: Eck H. V. , Taylor H. M.
Published: July 2010

Under limited water (preplant irrigation only), profile modification of Pullman silty clay loam to depths of 90 and 150 cm increased grain sorghum (Sorghum vulgare, Pers.) yields by 66.2 and 80.1%, respectively, over a 3‐year period. Modification (both 90 and 150 cm) increased water use efficiency in grain and total dry matter production by 41.3 and 25.2%, respectively. The increased yields and water use efficiencies resulted from changes in amount and distribution of stored water in the profile and from changes in plant rooting patterns.

Under adequate irrigation, profile modification had little effect on grain or stover yields but increased water use efficiency in two of three seasons.
Chemical Properties of Allophane from Hawaiian and Japanese Soils
Authors: Lai Sung‐ho , Swindale L. D.
Published: July 2010

Four moderately to strongly weathered soils from Hawaii and one moderately weathered soil from Japan, all derived from volcanic ash, were treated to separate out the allophane. The separates are described. With one exception, the fine clay fractions (<0.1µ) were almost X‐amorphous with only weak bands of 2:1 lattice clay minerals. The exception, the Waikaloa soil, contained much halloysite. Coarse‐clay fractions (2‐0.1µ) were mostly crystalline mica, kaolin and gibbsite. Differential thermograms of the amorphous fine clays were characteristic of allophane. The area of the low temperature endotherm correlated with the degree of crystallinity estimated from X‐ray data. Silica‐alumina molar ratios for the fine clays, varying from 0.927 to 1.50, were larger than the ratios for whole soils. The ratios for the three fine clays fractions which appeared least crystalline were all close to 1.0. Loss on ignition was inversely correlated with the silica‐alumina ratios. The allophane in these soils was fibrous and sponge‐like. The main infrared absorption band shifted from 9.70 to 10.29µ with increasing weight ratio of Al2O3/(Al2O3 + SiO2) and apparently reflected a change in state of coordination. Cation exchange capacities (CEC) of the separated fractions increased with increasing pH. There was a correlation between the apparent degree of crystallinity in X‐ray patterns of fine clays and the total change in CEC from pH 4 to pH 8.5. The CEC and infrared data together suggested that some stabilized AlIV‐O‐AlIV bonds occur in the allophane minerals.
Sodium‐Calcium Exchange Behavior in Organic Soils
Authors: Naylor D. V. , Overstreet Roy
Published: July 2010

The exchange complex of two organic soils from the Sacramento‐San Joaquin delta of California was easily saturated with calcium. However, the Ca2+ of the calcium‐saturated soil was difficult to replace with Na+ even when the calcium‐saturated soils were leached with 1N NaCl. Exchange of the Ca2+ by Na+ was found to be reasonably stoichiometric and complete after extensive leaching of the calcium‐saturated soils with the 1N NaCl solution. A large fraction of the adsorbed Ca2+ was extremely difficult to replace with Na+ when the soils were leached with large volumes of 0.01N NaCl.

The Ca‐Na ion‐exchange isotherms of the soils were determined through the use of Vanselow's and Gapon's ion‐exchange equations. Vanselow's ion‐exchange “constant” indicated an increased selectivity for Ca2+ over Na+ as the amount of exchangeable Na+ increased while Gapon's equation yielded a constant selectivity throughout the isotherms. Both equations suggested that the soils exhibit a very large selectivity for Ca2+ over Na+, especially as the amount of exchangeable sodium becomes appreciable.
Ionic Interaction in Diffusion
Authors: Frere M. H.
Published: July 2010

Analysis of the system of a plant root taking up ions at a constant rate shows that the apparent diffusion coefficient of each ion can change with time, distance from the root, composition of the solution, and the rates of uptake of all the ions. A numerical method, developed to include the electrical interaction of ions during diffusion, was used to simulate the concentration behavior in a sand culture. It is concluded that the assumption of constant diffusion coefficients in models of soil‐plant system can only be a first approximation.
Effect of Soil Potassium, Potassium Fertilizer, and Method of Placement Upon Lodging in Corn (Zea mays L.)
Authors: Walker W. M. , Parks W. L.
Published: July 2010

A quadratic regression equation including selected linear interactions was fitted to lodging percentages of corn grown on a Hartsells loam with varying K soil test levels and K fertilizer rates applied in the row and broadcast. The study was conducted over a 3‐year period and main effect variables for year, soil test K, and fertilizer K, as well as selected linear interactions, were included in a regression analysis. Both soil and fertilizer K significantly decreased percent lodging, and there was a significant difference in lodging among years. The significant soil K and fertilizer K interaction indicated that the effect of fertilizer K upon lodging varied with soil‐test level. There was also a significant interaction of fertilizer K with year indicating that the effect of K upon lodging varied among years.
Cotton Growth in an Acid Fragipan Subsoil: II. Effects of Soluble Calcium, Magnesium, and Aluminum on Roots and Tops
Authors: Soileau J. M. , Engelstad O. P. , Martin J. B.
Published: July 2010

Greenhouse and laboratory studies were made to evaluate the effects of soluble Ca, Mg, and Al on cotton (Gossypium hirsutum) growth in highly acid fragipan subsoil (Dickson series). Growth response was not related to soil pH, per se. The high level of soluble Al inherent in the Dickson subsoil greatly inhibited cotton growth by inducing morphological damage to the root system and by depressing uptake of Ca. Yield reductions were accompanied by Al concentrations above 0.2 and 0.02% in roots and tops, respectively. Severe Ca deficiency symptoms in tops and roots were observed where Ca was maintained at inherent subsoil levels and Al was either neutralized with base or was leached from the soil system. Although all treatment yields were not related to Ca or Mg concentrations in plant tissue, results suggested that the native levels of exchangeable Ca and Mg in Dickson fragipan subsoil may be limiting for cotton growth. Whether or not the “inherent” deficiency of Ca is entirely or only partly Al‐induced was not conclusively determined; however, this question may be relatively unimportant in view of the other harmful effects of high levels of soluble Al on cotton growth.
Effect and Interaction of Molybdenum and Limestone on Growth and Molybdenum Content of Cauliflower, Alfalfa, and Bromegrass on Acid Soils
Authors: Gupta Umesh C.
Published: July 2010

A greenhouse study involving four levels each of Mo and limestone indicated that without application of both Mo and lime, the cauliflower (Brassica oleracea, var. botrytis L.) crop produced very poor yields on the three soils investigated. Alfalfa (Medicago sativa L., var. ‘Narragansett’) was also a failure without added lime. At soil pH values of 5.5 and above, Mo applications increased the yield of alfalfa on Culloden sandy loam and O'Leary sandy clay loam soils, but gave no response on Acadia silty clay loam soil. Bromegrass (Bromus inermis Leyss., var. ‘Saratoga’) showed a marked response to application of lime, but very little response to application of Mo. Cauliflower yield showed a highly significant Mo × lime interaction on Culloden and O'Leary soils, where without added Mo, lime treatment up to pH 6.5 failed to show any increase in yield. Addition of different levels of lime did not change the exchangeable Mo content of any of the three soils, after growing crops.

The application of Mo or lime increased the Mo content of all crop tissues up to the highest level of applied Mo or lime. Application of lime substantially increased the Mo content of cauliflower and alfalfa while bromegrass showed less increase. There was a marked Mo × lime interaction on the Mo content of all crops, with much higher Mo contents in the plant when lime and Mo were applied together than when either treatment was applied alone. Liming to pH 6.5 without added Mo did not increase the Mo content of crops over 1.5 ppm.

In the absence of added Mo, cupping and drying of the edges of true leaves of cauliflower appeared at the early stage of growth whether or not lime had been applied to the soils. During the later stages of growth, these symptoms in most cases were associated with yellowing between the veins of leaves.
Inverse Formulation and Finite Difference Solution to Partially Saturated Seepage from Canals
Authors: Jeppson Roland W. , Nelson R. William
Published: July 2010

The mathematical model describing Darcian flow of water through soils approximates actual occurrences more closely when it permits regions of the flow to be partially saturated. A generally accepted relationship between effective permeability and capillary pressure is utilized to formulate and solve by inverse methods with finite differences the steady‐state flow system of water through soils. The inverse formulation considers the cartesian coordinates x and y as the dependent variables and the potential function ϕ and the two dimensional stream function ϕ as the independent variables (i.e. the problem is solved for x and y in the ϕψ plane). The approach is applied to the problem of seepage from a canal to a water table and a computer program (FORTRAN IV) has been written for solving this problem.
Cation Exchange Capacity and Weathering of Muscovite Macroflakes
Authors: Mokma D. L. , Syers J. K. , Jackson M. L.
Published: July 2010

The cation exchange capacity (CEC) of large (3‐ to 7‐cm2) muscovite macroflakes, determined with 45Ca, was 8.6 × 10‐7 meq/cm2 of geometrical surface, a value greater than the theoretical one of 3.5 × 10‐7 meq/cm2 calculated from the structural formula. The greater than theoretical CEC was attributed to exchange in areas of growth planes made accessible to the solution by (hkO) cleavage and by charged particle tracks. Similar values were obtained for BaEC (9.7 × 10‐7 meq/cm2) and CsEC (8.7 × 10‐7 meq/cm2). The excess of BaCl2, CsCl, or NaCl was not completely removed, whereas excess CaCl2 was removed, by five 100% methanol washings, as indicated by radiochemical measurements. The presence of excess BaCl2 and absence of CaCl2 were confirmed by electron micrographs of platinum‐carbon replicas of the muscovite cleavage surfaces, the former being removed by subsequent water washings. Hydrolysis of exchangeable Na was appreciable during water washings in the NaEC determinations, resulting in a considerably lower measured NaEC (1.1 × 10‐7 meq/cm2), but little hydrolysis of exchangeable Ba or Cs occurred in water washings. Electron micrographs showed that the muscovite (001) cleavage surfaces had been etched during extensive salt treatments and that a weathering product had formed on the surfaces. The latter material was insoluble in water, but was removed by treatment with Na citrate‐NaHCO3, indicating a sesquioxidic composition. The CEC of muscovite flakes was unaffected by the etching and the sesquioxidic weathering product.
Comparisons of Measured and Theoretical Mn2+ Concentrations in Soil Suspensions
Authors: Bohn H. L.
Published: July 2010

The Mn2+ concentrations in control and autoclaved suspensions of nine acid and alkaline soils in 0.01M CaCl2 differed widely from the Mn2+ concentrations calculated from models which either require measurement of Eh or assume Eh to be fixed by another redox couple. An alternative model is proposed which expresses the equilibrium solubility of the manganese compounds in terms of pH — ½pMn. The values of pH — ½pMn measured in the suspensions of all the soils tested correspond to the solubility of MnO2.
Evaluation of Slow‐Release Nitrogen Sources on Merion Kentucky Bluegrass
Authors: Moberg E. L. , Waddington D. V. , Duich J. M.
Published: July 2010

Various slow‐release nitrogen sources were used to fertilize ‘Merion’ Kentucky bluegrass (Poa pratensis L.) for two growing seasons. Slow‐release sources were ureaform, activated sewage sludge, ADM (a coated urea), Urex (a urea‐paraffin product), and IBDU (isobutylidene diurea). Response to fertilization was measured by weekly determinations of clipping yield and color rating. Urex performed similarly to ADM, and response following application was quicker and greater than that from ureaform, sewage sludge, and IBDU. IBDU showed good controlled release characteristics, but initial response after fertilization was slow. Residual effects of IBDU gave green color earlier in the spring than other treatments. Nitrogen recovery in the clippings was determined. Recovery ranged from 54% for ADM to 22% for ureaform over the 2‐year period. Recovery from sewage sludge was 27%. The highest recoveries for IBDU and Urex treated plots were 46% and 52%, respectively. Recovery from a urea treatment was 52%.
Thermal Conductivity and Diffusivity of Soil Using a Cylindrical Heat Source
Authors: Moench A. F. , Evans D. D.
Published: July 2010

The interference of moisture migration upon measurements of the thermal constants in soil has been reduced by using a large‐diameter, cylindrical thermal probe which is heated at a constant rate. Using the initial portion of the experimental record (temperature versus time) and by taking account of the thermal contact resistance between the heat source and sample material, it is possible to obtain values of thermal conductivity accurate to within 4%. Real thermal conductivity is obtained by subtracting from the measured value the small effect of distillation which is estimated with the help of the theory of vapor diffusion in porous media. Results obtained for a sandy loam soil show that real thermal conductivity increases rapidly with water content from 6.05 × 10‐4 cal/cm per °C per sec., when air dry, to 26.0 × 10‐4 cal/°C per cm per sec. at 30% of saturation. Thereafter it increases less rapidly (in proportion to the increase of volumetric heat capacity) to a value of 59.5 × 10‐4 cal/°C per cm per sec. at complete saturation. Real thermal diffusivity remains essentially constant at water contents above 30% of saturation. The method can also be used for rapid and accurate measurement of the thermal conductivity of liquids provided their volumetric heat capacities are known.
Thermodynamics of Copper(II)—Calcium Exchange on Bentonite Clay
Authors: El‐Sayed M. H. , Burau R. G. , Babcock K. L.
Published: July 2010

Thermodynamic parameters were derived for the exchange reaction between Cu(II) and calcium on bentonite clay in systems essentially devoid of precipitation, hydroxylation, and complex formation. Although the exchange isotherms showed preference of clay for calcium this proved to be only apparent since a large component of the standard free energy change for copper adsorption was due to entropy loss. The stronger binding of copper ions to clay surfaces was revealed, however, by the standard enthalpy changes and their arrangement in a more orderly structure than calcium ions on the surface was inferred from the magnitude of standard entropy changes. The activity coefficients of the adsorbed ions were obtained and were used to test the assumptions inherent in the treatment and the significance of their variations with clay composition was discussed.
Nutrient Cation Flows in Soil Around Plant Roots
Authors: Brewster J. L. , Tinker P. B.
Published: July 2010

The aim of the work was to test the relative importance of mass flow and diffusion in supplying nutrients to plant roots at different stages of growth, and whether there were, on average, important depletions or accumulations around the roots. Leeks (Allium porrum var. ‘Musselburgh’) were grown in large covered pots set in the field, and transpiration was measured by weighing. Nutrient content and root length were measured at four harvests, and soil solution composition was measured on 12 occasions. From this the mean inflows (uptake in moles/cm of root/sec) were calculated for K, Ca, Mg, and Na in three growth periods. They decreased strongly for sodium, slightly for potassium and magnesium, and remained constant for calcium.

The ‘apparent mass flow’ was taken as water inflow (ml/cm per sec) times soil solution concentration. It was small compared to total inflow for potassium, but increased with time; it was much larger than inflow for calcium, and slightly larger for magnesium and sodium.

The Passioura equation was used to calculate mean solution concentrations at the root surface. This indicated that the potassium concentration decreased to between 1/7 and ½ of the original, but that of Ca, Mg, and Na was slightly increased on average. Root demand coefficients ᾱr̄, are calculated from the results.
Nitrosation of Soil Organic Matter: III. Nature of Gases Produced by Reaction of Nitrite with Lignins, Humic Substances, and Phenolic Constituents Under Neutral and Slightly Acidic Conditions
Authors: Stevenson F. J. , Harrison R. M. , Wetselaar R. , Leeper R. A.
Published: July 2010

Molecular nitrogen, nitrous oxide (N2O), nitric oxide (NO), and CO2 were identified in the gases formed by reacting NO2‐ with soils, humic and fulvic acids, lignins, lignin‐building units, and polyphenols in aqueous buffer solutions of pH 6 and 7 in the absence of oxygen. The composition of the mixture of gases was dependent upon the nature of the material examined, with relatively larger amounts of N2 being produced from the humic and fulvic acids. Compounds containing methoxyl groups failed to yield detectable amounts of methyl nitrite (CH3ONO) at the pH levels found in most soils. The reaction of NO with humic substances in the absence of oxygen led to the production of N2O and CO2.
Volatilization of Lindane and DDT from Soils
Authors: Guenzi W. D. , Beard W. E.
Published: July 2010

Four soils ranging in texture from a loamy sand to a clay were amended separately with 14C‐labeled lindane and DDT to give a concentration of 10 ppm. Pesticide volatilization was determined each day for three consecutive drying cycles at 30C and 55C by liquid scintillation counting of trapped pesticide vapors. Soils were initially wetted to ⅓ bar suction and dried by passing dry air over the soil surface.

Neither pesticide was volatilized at either temperature after the soils contained less than a monolayer of water. Since these soils became dry at different times during the 14‐day drying cycle, two factors were important in describing pesticide volatilization. First, the rate of pesticide loss was constant for each soil in the moisture range from ⅓ bar to 15 bars. Second, since essentially the same amount of water was lost from each soil per day until dryness, the pesticides were volatilized over a longer period of time from the finer textured soil than from the coarser textured soils. A mechanism is proposed.

Volatilization rates for DDT and lindane from soil containing moisture greater than 15 bars tension were dependent on temperature, adsorptive characteristics of the soil, and concentraction of the pesticide (lindane). For lindane and DDT at 30C, the rate of volatilization from soil was in the order Valentine loamy sand > Hand loam > Raber silty clay loam > Promise clay.

Degradation of lindane to PCCH occurred at 30C and 55C. After three wetting and drying cycles at 55C, the amount of DDT converted to DDE ranged from 6.7% for Valentine loamy sand to 21.2% for the Raber silty clay loam.
Micromorphology of Soil Fabric at Tree Root‐Soil Interface
Authors: Blevins R. L. , Holowaychuk N. , Wilding L. P.
Published: July 2010

The influence of tree roots on physical properties and spatial arrangement of adjacent soil materials were studied. Soil fabric in the vicinity of tree root‐soil interface was observed microscopically using specially prepared soil thin sections from samples obtained from forest soils by a freezing in situ technique. Micromorphological observations showed that within the 0‐ to 0.4‐mm radial interval from the root‐soil interface there was a relative decrease in grains and pores > 20µ. An increase in oriented clay, and percentage elongate grains oriented within 30° tangent to the root surface was observed. These features imply that the matrix adjacent to tree roots (within 1 to 2 mm) contain more fine‐grained materials, with a consequent pore‐size distribution shift toward smaller pore diameters (20–50µ or less). Microscopic measurement of pore size distribution compared closely to aeration porosity values calculated from bulk density, particle density, and moisture content at 60‐cm tension data. Percent pores determined microscopically on soil thin sections without reference to distances from soil‐root interfaces agreed closely with values measured at a distance interval of 2.0 to 4.0 mm from root‐soil interface. Aeration porosity, measured microscopically in the area of close proximity to actively growing roots at time of sampling, was very low.

These data and inferences suggest that physical properties of the soil contiguous to a tree root may differ appreciably from such factors farther away from the root.
Gaseous Diffusion Evaluation in Forest Humus
Authors: Ballard T. M.
Published: July 2010

Penman's ratio of direct length to effective diffusion path length, L/Le, is not directly predictable from the air content of forest humus, probably because of anisotropic pore orientation. The diffusion coefficient of a gas in the unsaturated porous medium can be estimated from temperature, air pressure, porosity, water content, and an empirically determined value of L/Le. A steady state CO2 diffusion method is proposed for measuring L/Le and gaseous diffusion coefficient in either loose or structurally intact forest humus samples.
Freezing and Thawing Effects on Drainage
Authors: Benoit G. R. , Bornstein J.
Published: July 2010

Laboratory studies were conducted on insulated models containing coarse sand (1–2 mm), fine sand (0.5–1 mm) and soil (0–2 mm and 2–4.8 mm) to determine the effects of freezing and thawing on sloping land drainage. Interrelations between structure and texture, rates and extent of ice formation, and rates and magnitudes of drainage were determined. Decreasing temperatures and subsequent ice formation decreased the relative mobility of water, thereby increasing water retention and decreasing rates of water transmission. The magnitude of the short‐term, freeze‐thaw effects on soil water retention and transmission was influenced by soil aggregate size, aggregate stability, and soil water content during freezing. On a long‐term basis, drainage that results in a consistently lower water content during freeze‐thaw cycles may lead to a changed soil structure and thus a changed drainage requirement.
A Gamma‐photoneutron Method for Laboratory Studies of Soil Water
Authors: Corey J. C. , Hawkins R. H. , Overman R. F.
Published: July 2010

The gamma‐photoneutron method is unique among nuclear methods used to study water movement in soil because the heavy water (2H2O) content of laboratory soil columns can be measured independently of bulk density of soil, soil texture, light water (1H2O) content, and type of clay mineral. The method requires a radioactive source that emits gamma photons in excess of 2.23 Mev and a neutron detector. The neutron detector measures photoneutrons produced when the deuterium nuclei in the gamma radiation field split into a photoneutron and a proton. The number of photoneutrons detected is linearly related to the heavy water content of the soil column.
Comparison of Inorganic Nitrogen Contents of Undisturbed, Cultivated, and Barnyard Soil Profiles in Wisconsin
Authors: Olsen R. J. , Hensler R. F. , Attoe O. J. , Witzel S. A.
Published: July 2010

In a group of 25 soil profiles, the total content of NO3‐N to a depth of 240 cm was about 55, 230, 165, and 135 kg/ha for the undisturbed, cultivated, poorly‐drained, and well‐drained barnyard profiles, respectively, and 35, 30, 995, and 240 kg/ha for exchangeable NH4‐N. Similarly, the average concentration of NO3‐N in the soil solution at the 180–240 cm depth was 8, 11, 9, and 11 ppm. The concentration tended to decrease with soil depth, apparently due to plant uptake, denitrification, and microbial immobilization processes. The total content of NO2‐N to the 240‐cm depth ranged from 6 to 25 kg/ha.
Conditions Affecting Cesium Fixation and Sodium Entrapment in Hydrobiotite and Vermiculite
Authors: Klobe W. D. , Gast R. G.
Published: July 2010

The effect of residual and added K on Cs fixation was studied, using samples of K‐extracted Transvaal, South African hydrobiotite with 66, 60, 23, and < 1% K saturations. Fixation was measured by the availability of the cations for rapid isotopic exchange in a well‐stirred system.

Over 95% of the sorbed Cs was fixed above 1% Cs saturation of the exchange capacity regardless of K levels or whether the K was in the form of residual K in hydrobiotite or K added to the vermiculite prior to addition of the Cs. In contrast, trace levels of Cs (i.e., carrier‐free 137Cs) were fixed to a much lesser extent, indicating that it may be more available for plant uptake.

X‐ray and Na entrapment results indicate that Cs saturations below 40% of the exchange capacity result largely in interstratified Na‐ and Cs‐rich layers with little edge collapse. Higher Cs saturations resulted in increased edge collapse and Na entrapment. Formation of interstratified layers vs. edge collapse of the particles tends to be associated with smaller and larger particles, respectively.
Comparison of Organic Matter Destruction by Hydrogen Peroxide and Sodium Hypochlorite and Its Effects on Selected Mineral Constituents
Authors: Lavkulich L. M. , Wiens J. H.
Published: July 2010

The destruction of organic matter from widely different soils was evaluated by using hydrogen peroxide and sodium hypochlorite oxidation procedures. The amounts of extractable Si, Mn, Al, and Fe were determined on the residues following treatment with the oxidizing agents by using acid ammonium oxalate and 0.5N NaOH extraction procedures. In addition, the amount of Si, Mn, Fe, and Al in the extracting solutions was determined. It was found that NaOCl extracted more organic matter with less destruction of the oxides than procedures employing H2O2. This was substantiated statistically using the t‐test as applied to paired values. Three treatments with NaOCl were concluded to be satisfactory for destruction of organic matter with minimum removal of Si, Mn, Fe, and Al.
The Characteristics, Classification and Genesis of Some Tropical Spodosols
Authors: Tan K. H. , Perkins H. F. , McCreery R. A.
Published: July 2010

Morphological, chemical, and mineralogical properties are presented for three tropical spodosols. Based on the occurrence in different climatic zones, the soils were distinguished as lowland podzols and mountain or highland podzols.

The lowland podzol had a low organic matter content, a weakly developed Bh and a well developed argillic horizon below the spodic horizon. The name Humic Alfic Tropoferrod is proposed for this type of podzol. The A horizon contained predominantly amorphous clay, but the B horizon had appreciable amounts of kaolinite.

Highland podzol I was high in organic matter, had a well developed Bh, but lacked an argillic horizon, and was classified as a Typic Tropohumod. Highland podzol II had similar properties, but was relatively young in degree of development and was classified as an Entic Tropohumod. The clay fraction of the humods was characterized by high amounts of amorphous clay, probably allophane. Kaolinite was not detected.
Tensile Strength of Clay Films: A Measuring Technique
Authors: Dowdy R. H. , Larson W. E.
Published: July 2010

A technique is presented for quantitatively measuring tensile strength and axial tensile strain of clay films over a relative water vapor pressure range (P/P0) from 0.02 to 0.92. The tensile strain energy is calculated from these data. With this technique, relative electrostatic and chemical interactions of different clay systems can be assessed with a minimum interference from frictional force components. Data for Mg‐mont‐morillonite showed a maximum tensile strength of 210 kg cm‐2 at P/P0 = 0.02, exhibited an axial strain of 173µ cm‐1 and required 0.22 joules cm‐3 of tensile strain energy to rupture.