bluuebunny/crossref_metadata_2025 huggingface dataset:
The Importance of Illite as a Source of Potassium in Nebraska Soils
Authors: Abed Fawzi M. A. H. , Drew James V.
Published: July 2010

The uptake of nonexchangeable K by alfalfa (Medicago sativa L.) from samples of the surface layers of 8 Nebraska soils in a greenhouse experiment was more closely related to illite contributed to the soils by fine silt (r = 0.85) than to K‐bearing minerals contributed to the soils by other separates. Measurements of exchangeable K may underestimate the K‐supplying power of Nebraska soils for alfalfa when relatively large amounts of illite are contributed to the soils by fine silt.
Soil Phosphorus in South Dakota: II. Comparisons of Two Availability Tests with Inorganic Phosphorus Fractions Among Soil Series
Authors: Westin F. C. , Buntley G. J.
Published: July 2010

Linear correlations are presented to compare the Bray and Olsen availability tests for soil phosphorus with four inorganic P fractions, clay content, and pH. The soils represent two great soil groups, several general profile textures, several parent materials, and three horizons.

Although trends are indicated when general profile textures, parent materials, and horizons are considered separately, the clearest relationship between the availability tests and the four inorganic P fractions is with great soil group. When all Chernozem samples are considered together the Bray method gives higher positive correlations with the P fractions than the Olsen method. For Chestnut soils considered together the Olsen method gives higher positive correlations than the Bray method. Only one correlation among the Chernozem and Chestnut soils had a significant z value, however. Among the Chernozems when the r values of the textures, parent materials, and horizons are placed within their appropriate great soil group the Bray method has higher r values for 28 of the 31 positive correlations involved. Two of these had significantly higher r values as determined by the z test. When this procedure is followed for the Chestnuts the Olsen method has higher r values for 18 of the 29 positive correlations involved. Eleven of these correlations had significant z values.

Clay content, pH, and Ca‐P generally were involved in more negative than positive correlations with the Olsen and Bray methods with the Chernozem and Chestnut soils. The difference in the behavior of the Bray and Olsen reagents between the Chernozem and Chestnut soils used in this study probably is related to climate and its influence on the degree of development of the two great soil groups involved.
Periodic Sedimentation and Soil Formation on an Alluvial‐Fan Piedmont in Southern New Mexico
Authors: Gile L. H. , Hawley J. W.
Published: July 2010

Gullies cut in alluvial‐fan piedmont deposits at the southern end of the Jornada del Muerto basin, New Mexico, reveal evidence of periodic sedimentation and soil formation. The gullies show a succession of four major sediments, each of which has a distinct soil, indicating that each period of sediment deposition was followed by a period of stability and soil formation. The two youngest sediments are restricted primarily to a broad drainageway position and have soils with relatively weak Bt and carbonate horizons. The next older sediment, buried in the broad drainageway, has a soil that has prominent textural B and carbonate horizons and that emerges at the land surface on either side of the drainageway. Towards the basin axis the sediments thin and there is mergence of the land‐surface soil with the oldest soil exposed in the gullies.

The land‐surface soils overlie much older soils and in places are so thin that the buried soils must be considered in classification of the land‐surface soils. Gradual mergence zones of major sediments can conceal complexities greater than might be suggested by the generally smooth relief. Filling of channels in old sediments by younger sediments can cause prominent and abrupt soil changes not suggested by the smooth relief and uniform slope which crosses the soil boundaries. These phenomena are especially prevalent in and adjacent to drainageways and in areas of thinning of major sediments.
Selection of Characteristics for Numerical Classification of Soils
Authors: Sarkar P. K. , Bidwell O. W. , Marcus L. F.
Published: July 2010

Eighteen hundred and thirty product‐moment correlation coefficients were used to select characteristics from 61 given soil characteristics for numerical classification by electronic computer of 26 soils representing nine Orders of the new soil classification system (7th Approximation). Correlated characters were eliminated successively to 51, 40, 33, and 22 soil characteristics according to decreasing levels of the product‐moment correlation coefficient over soils.

The correlation method is an objective procedure for eliminating members of groups of similar characteristics that might produce undue weighting in the numerical classification. It is superior to the heretofore used, and often criticized, method of selection based on subjective evaluation of the characteristics in soil classification.
Relation of Field‐Plot Runoff to Management and Physical Factors
Authors: Wischmeier W. H.
Published: July 2010

The detailed data for runoff analysis were assembled from nearly all erosion plot studies in the United States. Individual study averages of runoff from cropped plots have ranged from 3% to 36% of total precipitation, from 1 to 14 inches annually. Analyses indicted factor relations valuable for predicting water yields from cropland areas. Improved soil and crop management reduced average plot runoff about 40%. An inverse, curvilinear relation of runoff from growing and maturing corn (Zea mays L.) to crop yield was highly significant. At moderate fertility level, runoff reduction by contour tillage averaged slightly more than 15%. Under natural field conditions, runoff from row crops averaged a 10% increase for each additional percent slope. The relationship is expressed by: log W = 0.521 + .041s, where W is inches runoff and s is percent slope. Slope effect decreases as the surface becomes smooth and approaches zero for dense meadow or saturated soils. Effect of slope length on annual runoff was usually insignificant, but some transmission losses in the growing season and acquisitions in the dormant season were indicated. For 35 fallow soils with sand contents ranging from 4% to 66%, runoff was inversely proportional to organic matter content but was little affected by differences in particle size distribution.
Formation of Surface Coatings on Limestone Particles in Soils
Authors: Barrows H. L. , Simpson E. C. , Tu H. Y.
Published: July 2010

High‐purity, 12‐ to 14‐mesh calcite limestone was mixed into acid soils containing relatively large amounts of either P, Al, or Mn. These mixtures were equilibrated for 12 months, undergoing wetting and partial drying cycles. Samples of each mixture were withdrawn periodically, and the limestone particles were recovered and examined.

The surface of particles equilibrated in the high‐P soil developed a porous, white granular coating. Ater 7 months' equilibration, this coating varied from about 0.03 to 0.1 mm in thickness. It was concluded that the coating formed through the combined processes of weathering, recrystallization of calcite, and adsorption and/or precipitation of phosphates from the soil.
Effect of Sulfur Content of Straws on Rates of Decomposition and Plant Growth
Authors: Stewart B. A. , Porter L. K. , Viets F. G.
Published: July 2010

Sulfur deficiency must be considered in management of crop residues. With adequate N, P, and K, the decomposition rate of straw in soil low in sulfates depended on the S content of the straw. Incubation studies showed that unless S fertilizer is added, the S content of straw must exceed about 0.15% for a maximum rate of straw decomposition. Growth of winter wheat (Triticum aestivum L. ‘Wichita’), in the greenhouse, on a NPK‐fertilized soil was governed by the S content of straw mixed in the soil. Straws with < 0.15% S added to soil depressed wheat growth, but straws with a higher S content increased yields compared to the no‐straw treatment. When S was added along with N, P, and K, the S content of the straws had no effect on wheat growth.
A Technique for Continuous Monitoring of pH in Soil Systems
Authors: Papendick R. I. , Giordano P. M.
Published: July 2010

A technique is described for continuous in situ measurement of pH in soil systems. The instrumentation consists of several minature combination electrodes connected through a stepping switch arrangement to an amplifier and a single‐point recorder. The unit is not subject to external disturbances and is applicable to situations where information concerning rate and degree of pH change is desired. A description of the system and an experimental example of its use are discussed.
Effect of Phosphorus on Some Physical Properties of Soils: II. Water Retention
Authors: Lutz J. F. , Pinto Rafael A. , Garcia‐Lagos Ricardo , Hilton H. Gill
Published: July 2010

Field studies showed that the use of phosphate fertilizers increased the amount of water present in the soil and facilitated tillage. Crop yields were closely related to the increased water content. Laboratory studies showed that P appreciably increased the water‐holding properties of soils. This was found to be directly related to the increase in the negative charge of the soil particles and the charge was closely related to the Al‐phosphate/Fe‐phosphate ratio. In general increases in water‐holding capacity were caused only by the larger rates of P, but in some instances 50 ppm P gave significant increases.
Determination and Isotope‐Ratio Analysis of Different Forms of Nitrogen in Soils: 2. A Simplified Procedure for Isotope‐Ratio Analysis of Soil Nitrogen
Authors: Cheng H. H. , Bremner J. M.
Published: July 2010

A procedure for isotope‐ratio analysis of soil nitrogen is described which eliminates the ammonium distillation stage of the customary procedure. The nitrogen in the soil sample is converted to ammonium by Kjeldahl digestion without use of a catalyst, digestion being accomplished by heating the sample with sulfuric acid containing a high concentration of potassium sulfate (ca. 0.7g/ml of H2SO4). An aliquot of the digest is partially neutralized and treated in vacuo with alkaline hypobromiteiodide solution, and the N2 liberated by this treatment is analyzed by the mass spectrometer. This simplified procedure eliminates problems encountered in distillation and concentration of ammonium samples for N15 analysis and gives the same results as the customary procedure.
Nutrition of Corn (Zea mays L.) on a Calcareous Soil: III. Interaction of Zinc and Boron with Plant Population and the Relationship between Grain Yield and Leaf Composition
Authors: Fuehring H. D.
Published: July 2010

A field experiment on corn with N, Zn, Mn, B and plant population as variables resulted in important positive interactions of plant population with applied Zn and with applied B indicating that limited Zn or B may be part of the reason for the severe yield decrease resulting from planting corn too thickly. High rates of applied Zn or B (90–180 kg/ha) were depressing to grain yield at low plant populations (40,000–53,333 plants/ha) but increased yields at high plant populations (80,000–93,333 plants/ha).

The logarithm of the nitrate‐N concentration of the midrib of the sixth corn leaf at the silking stage was found to be closely correlated with grain yield up to about 1,000 ppm. The relationship between the total N concentration of the leaf blades and grain yield was less distinct. The phosphate‐P concentration of the midrib and the total P concentration of the leaf blades were significantly increased by increasing applications of N. The B concentration of midribs at the point of maximum yield varied from < 60 ppm at low plant population to 120 ppm at high plant population.
Clay‐Suspension Root‐Coating as Antidesiccants and Rhizospheric Nutrient Sources
Authors: Tabor C. A. , Davey C. B.
Published: July 2010

Suspensions of kaolinitic and montmorillonitic clays were applied to roots of loblolly pine seedlings (Pinus taeda L.). Survival and growth effects of these clay‐suspension, root‐coatings were evaluated in a series of greenhouse experiments. Preplanting exposures to adverse atmospheric conditions of clay‐treated seedlings showed positive effects of the clays as antidesiccants. Clay coatings did not appreciably influence early growth under conditions of either high or low soil moisture stress. Seedlings from three known mother trees were grown in subirrigated sand cultures using Ca2+‐, Mg2+‐, K+‐, and Na+‐saturated clays as sources of the specific cation of each treatment. Seedling responses varied according to the clay used, the cation charge, the physiological role of the cation, and the genetic source of the seed. The higher cation exchange capacity (CEC) clay, montmorillonite, appeared to have a potential use as a rhizospheric nutrient source.
The Effect of Interactions of Salts and Clays on Unsaturated Water Flow
Authors: Christenson D. R. , Ferguson Hayden
Published: July 2010

Artificial soils containing 17.6% dickite or montmorillonite clay minerals were treated to give exchangeable sodium percentages (ESP) of 5.0 and 20.3, and 5.5 and 13.6, respectively. Calcium chloride solutions of 0 or 0.015 meq/ml were applied to horizontal columns of the soils at 2 millibars tension. Deviation of the least squares line fit to data of quantity of water entry or distance of water movement vs. √time from 0 at time = 0 was taken as an indication of swelling. By this criteria, swelling was not a factor in water movement in dickite soil regardless of treatment but was a factor in water movement in montmorillonite soil. Use of 0.015NCaCl2 solution eliminated swelling in the 5.5 ESP montmorillonite soil but only reduced swelling in the 13.6 ESP soil.

Water diffusivities were calculated from water content vs. distance curves. Use of 0.015N CaCl2 increased water diffusivity by a factor of at least 1.8 in all soils except montmorillonite ESP 13.6. This is probably associated with a reduced influence of the double layer on water movement as well as a change in pore geometry. By the method of calculations, use of 0.015N CaCl2 did not increase the diffusivity of montmorillonite ESP 13.6 over that of distilled water in spite of reduced swelling.

Both water treatments resulted in some Na displacement from the first few centimeters of the columns and movement with the wetted front, but the quantity of Na movement was much greater with the CaCl2 solution.
Infiltration and Redistribution of Water in Vertical Columns of Loam Soil
Authors: Staple W. J.
Published: July 2010

A numerical method was used to compute infiltration and redistribution of water in vertical columns of air‐dry Grenville silt loam. Hysteresis was taken into account in that drying tensions and hydraulic conductivities were interpolated from the appropriate scanning curves at each depth in the upper profile as redistribution continued into the dry soil below.

Although the computations were not confirmed by independent experiments, results from related measurements showed that the distribution curves were of the right magnitude. The moisture contents reached in the drying zone after 24 to 72 hours' redistribution were in agreement with field capacity data.

Computed moisture contents following redistribution in which hysteresis in both tension and conductivity were neglected differed considerably from the accepted hysteresis‐dependent values. Computed moisture contents in which hysteresis in conductivities only were neglected were closer to the accepted values when conductivities for wetting were used.
Surface Mobilities of Cations in Clays
Authors: Cremers A. E. , Laudelout H.
Published: July 2010

The effect of clay content and temperature on the electrica conductivity of two Na‐kao inite clays is investigated. The effect of the type of cation is examined in the Camp‐Berteau montmorillonite. The ionic surface mobilities (i.e. corrected for tortuosity effects) are calculated from the conductivity results. In Na‐kaolinite clays, surface mobility steadily increases with increasing cay content and attains about 40% of its solution value when clay content becomes about 70% by weight. In montmorillonite clays, surface mobility increases until clay content reaches about 35% by weight. Higher clay contents result in nearly constant values for the surface mobilities. In the series of alkali metal cations, surface mobilities increase from Cs+ (attains about 7% of its solution value at 55% clay) to Na+ (attains about 60% of its solution value at 55% clay); activation energies increase from Na+ (4.6 kcal/eq. at 55% clay) to Cs+ (5.6 kcal/eq at 55% clay).

The ionic mobilities and activation energies can be correlated with the polarizabilities of the ions. It is suggested that the mobility of an ion along a clay surface is influenced more by crystallographic than by hydrated ionic volume. The large negative entropies of activation, calculated on the basis of the transition theory of rate processes, are interpreted in terms of hydration effects when an ion moves from one site to another.

The agreement between self‐diffusion coefficients calculated from the electrical conductivity data and the values which may be found in the literature is very good. The applicability of the electrical conductivity method for investigating purely geometrical effects is discussed.
Management of Nonleguminous Green Manures and Crop Residues to Improve the Infiltration Rate of an Irrigated Soil
Authors: Williams William A.
Published: July 2010

The effects of nonleguminous green manures and crop residues on the rate of infiltration were studied in field experiments on an irrigated soil.

The increase in infiltration rate resulting from the green manure species was inversely related to their nitrogen concentration at the time of incorporation. The effect of the low nitrogen green manures persisted throughout the 28‐month trial period. Nitrogen fertilization of crop residue reduced infiltration rate in one experiment, but had no significant effect in another. Barley (Hordeum vulgare) crop residue and the resultant increase in infiltration rate were associated with an increase of 7 cwt of sugar produced/acre by the following crop of sugar beet (Beta vulgaris).
Moisture Release Characteristics of Forested Sand Entisols In Northern Lower Michigan
Authors: Zahner Robert , Hedrich David R.
Published: July 2010

Forest growth is better on Grayling fine sand than on Grayling medium sand. Moisture release curves were constructed for samples from these two types and for pure sand fractions separated from the samples. Examples of the fine sand soil retained 10% and the medium sand soil retained 7% water by weight at field capacity (.06 atm tension), while both soils retained equal amounts, 2.5%, of water at 15 atm tension. Of the pure sand fractions, very fine sand retained substantially more water at low tensions than did the larger fractions amounting to more than five times the amount of readily available water. The fine sand soil type contained six times the amount of very fine sand fraction than did the medium sand soil type, 12% vs. 2% by weight. Thus, much of the difference in water retention between the two examples is attributed to the very fine sand fraction, probably also accounting for much of the difference in tree growth.
A Portable Low‐Intensity Rain Simulator for Field and Laboratory Use
Authors: Steinhardt Reuven , Hillel Daniel
Published: July 2010

A design is presented for construction of a dripping‐type rain simulator that is useful for study of infiltration characteristics of surface‐crusted soils and comparison of surface treatments for runoff inducement. The apparatus is lightweight, portable, and easily assumbled. Rain intensity can be varied between 4 and 100 mm/hr with adequate uniformity of distribution. Raindrop size and impact velocity, as well as rainfall intensity, can be controlled independently.
Soil Freezing and Soil Water Characteristic Curves
Authors: Koopmans R. W. R. , Miller R. D.
Published: July 2010

An earlier paper suggested that the soil water characteristic (SWC) of soil should have an analogue to be called the soil freezing characteristic (SFC) that could be obtained by freezing saturated soil in an apparatus functionally related to the pressure plate apparatus. The analogy for granular soil, free of colloids, is on a different basis (capillary effects) than for soil that is wholly colloidal (absorption effects). Different rules are needed to demonstrate the analogies for the respective types. Apparatus was devised to permit SFC and SWC data to be obtained, in turn, with each material placed in the apparatus. Two silt fractions, a sodium‐montmorillonite paste, and a whole soil were used. The results confirm the expected analogies and indicate that in these experiments, the ratio of the specific surface energy of an airwater interface at 20C to that of an ice‐water interface near 0C was as 72.7:33.1. The results demonstrate significant mobility for unfrozen water at temperatures as low as −0.15C even in clean silt fractions. It is concluded that the inherent instability of some of the residual water in soils during drying does not significantly affect the SWC in the range 0 to 4 bars of matric suction.
Soil Adsorption of Linear Alkylate Sulfonate
Authors: Murti G. S. R. Krishna , Volk V. V. , Jackson M. L.
Published: July 2010

Linear alkylate sulfonate (LAS) adsorption was studied in relation to the pH, cation‐exchange capacity, clay, organic matter, extractable Fe and Al, exchangeable Al, and Fe2O3 contents of several soils. The LAS adsorption correlated highly significantly with the organic matter content (r = 0.81) and the P fixing capacity (r = 0.75) of the soils. With the removal of sesquioxides as the final pretreatment on chloritic, kaolinitic and allophanic soils the LAS adsorption decreased from values of 19 to 48 µ g/g on the untreated soil to a value of zero. When treated with a terminal H2O2 treatment, the adsorption values on the same soils ranged from 17 to 65 µ g/g. The increase apparently occurred as a result of Fe and Al released from organic chelates. The increase in the LAS adsorption from 7 to 27 µ g/g on the untreated soil to 8 to 50 µ g/g after the removal of both the organic matter and sesquioxides in a number of montmorillonitic Wisconsin soils indicates the importance of montmorillonite in LAS adsorption.
Conductance of Adsorbed Alkali Cations in Aqueous and Alcoholic Bentonite Pastes
Authors: Shainberg Isaac , Kemper W. D.
Published: July 2010

Equivalent conductivities of the alkali cations adsorbed on bentonite clay in water, and in methanol and ethanol gels, were determined and compared with their equivalent conductivities in bulk solution. The mobilities of adsorbed cations were reduced to about one‐half their mobilities in bulk solution in water systems and to much smaller fractions of their bulk solution mobilities in alcohol gels. The reduction in mobility was independent of the clay concentration in the range studied, and was characteristic of the cation. It was pointed out that “specific forces” between the cation and the clay surface are not possible unless the cations reside directly on the clay surface (without a watermolecule between the ion and the clay). The fraction of adsorbed cations not participating in electrical transport was in reasonable agreement with the portion of adsorbed ions residing directly on the surface as calculated considering both hydration and electrical potential energies in the Boltzmann distribution equation. An electrostatic interaction is discussed which would cause reduction in mobility of cations that are in the first molecular layer of solvent.
Ionic Relationships in the Pedogenesis of Hawaiian Soils
Authors: Swindale L. D. , Uehara G.
Published: July 2010

A pedogenic mica is believed to be present in a sequence of Hawaiian soils, the lower, drier members of which are Oxisols and the upper, wetter members Ultisols. The mica decreases with depth within each soil and increases generally with increasing rainfall and elevation. Direct relationships exist between the amount of mica in the soils and the amount of exchangeable potassium per unit of base saturation, and between the amount of mica and the concentration of potassium in the soil solution. The parameters, log [K+]/[H+] and log [H4SiO4], of the mass action equations between mica, kaolin, and gibbsite, when measured for the soil solutions, are useful indicators of the probable stabilities of the minerals in the soils. Tests of physical models of the chemical system involved indicate that the exchangeable potassium and the potassium in the soil solutions as measured are not in equilibrium with the minerals in the soils.
Fractionation and Characterization of Naturally Occurring Organo‐Clay Complexes
Authors: Arshad M. A. , Lowe L. E.
Published: July 2010

Clay separated from a Solonetz Bnt horizon was fractionated lnto coarse (2–0.2 µ), medium (0.2–0.14 µ), fine (0.14–0.08 µ) and very fine (<0.08 µ) size fractions. Organic matter from these fractions was obtained by extractions with 0.1M Na4P2O7 (pH 11.0), followed by extractions with 0.1N NaOH. The residue was then repeatedly treated with an HF‐HCl mixture and the remaining organic fraction was extracted with 0.1M Na4P2O7 (pH 11.0). The organic and clay fractions were analyzed for C and N contents, and by X‐ray diffraction, electron microscopy and infrared spectroscopy.

Experimental data indicated that the largest portion of the complexed organic matter was associated with the coarse clay fraction which contained relatively large amounts of kaolinite, whereas a small percentage was associated with the fine clay fraction where kaolinite occurred as traces. The percentage of extractable organic matter increased with decrease in clay particle size. No evidence was found for the adsorption of organic matter in the interlamellar spaces as reported by some previous workers.

Study of humic acids isolated from the clay fractions showed that aliphatic structures were more common in humic acids derived from fine clay than in those separated from the coarse clay fraction. Aromatic structures of the humic acids increased in the order of pyrophosphate humic acid→alkali humic acid→residual humic acid. The humic acids unextractable by the solvents commonly employed appeared to be highly humified and aromatic in nature.
Numerical Method for Analyzing Hysteresis‐Affected, Post‐Infiltration Redistribution of Soil Moisture
Authors: Rubin J.
Published: July 2010

An especially devised numerical procedure applied to the Darcian model of soil moisture flow makes it possible to analyze the post‐infiltration redistribution of water in semi‐infinite, vertical soil columns. The method takes into account the effects of hysteresis by making it possible to find, within the hysteretic system of curves, the unique curve which characterizes moisture transformations at each soil depth. The method can be applied to cases in which the moisture flux at soil surface is zero as well as to those in which the redistribut on is accompanied by constantrate evaporation.

The results obtained by applying the new method to data on moisture retention and conductivity of a sandy soil demonstrate the importance of hysteresis in the redistribution processes.
Analysis of Gamma‐Ray Spectra From Soils and Plants: II. Effect of Trees on the Distribution of Fallout
Authors: Franklin R. E. , Gersper P. L. , Holowaychuk N.
Published: July 2010

A detailed study of the distribution of fallout in soil from a forested area has been initiated. Surface soil samples (0 to 7.5 cm) collected at several distances from the stems of beech‐(Fagus grandifolia), sugar maple (Acer saccharum), tulip (Liriodendron tulipfera), scarlet oak (Quercus coccinea), hickory (Carya glabra), and white oak (Quercus alba) trees were analyzed by gamma‐ray spectroscopy. The concentration of Cs137 in the soil near the stem of a beech tree was about five times higher than at other positions under the canopy. This effect was about one‐half as great for sugar maple and much less for the other species. The magnitude of this concentration is apparently related to the quantity of stemflow water, which may be appreciable with some species and negligible with others. Samples collected at four depth intervals (0 to 7.5, 7.5 to 15, 15 to 22.5 and 22.5 to 30 cm), in an area which included three of the trees, were also analyzed. Considerable leaching of Cs137 occurred in soil adjacent to tree stems, apparently as a result of stemflow.
Atrazine Hydrolysis in Soil
Authors: Armstrong D. E. , Chesters G. , Harris R. F.
Published: July 2010

An important pathway of atrazine degradation in perfusion systems of three soils was chemical hydrolysis to hydroxyatrazine. Ultraviolet spectrophotometric analyses of the perfusates showed the presence and accumulation of hydroxyatrazine. Atrazine degradation followed first‐order kinetics in soil‐free, sterilized soil and perfusion systems. An increased rate of atrazine hydrolysis in an acid soil was consistent with the effect of pH on hydrolysis. No microbial degradation of atrazine was detected following inoculation of a soil‐free atrazine medium with perfusates. An increased rate of hydrolysis in the presence of sterilized soil was postulated to result from soil adsorption of atrazine. Soil pH and organic matter content largely controlled the rate of atrazine hydrolysis; for soils of similar pH, atrazine degradation rates increased with increased atrazine adsorption.
Extraction of Organic Nitrogen and Ammonium From Soil with Hydrofluoric Acid
Authors: Stevenson F. J. , Kidder G. , Tilo S. N.
Published: July 2010

From about one‐fifth to one‐half of the organic N in some surface soils, and over two‐thirds of that in some subsurface soils, occurred in compounds capable of being extracted with HF. The NH4+‐N/organic N ratios in HF extracts were generally highest in soils where the predominant clay minerals were illitic, intermediate in soils where the predominant clay minerals were montmorillonitic, and lowest in soils where the clay fraction contained high amounts of amorphous (allophanic) material. The presence of organic N compounds within the lattice structures of clay minerals was indicated. Analyses of the Morrow Plot soils showed that a considerably higher fraction of the organic N in the heavily cropped soils was extractable with HF than in soils where organic matter had been maintained at high levels by periodic application of manure or through growth of legumes. Evidence was obtained in support of the view that many soils contain significant amounts of naturally occurring fixed NH4+.
Some Till‐Derived Chernozem Soils in Eastern North Dakota: I. Morphology, Genesis, and Classification
Authors: Redmond C. E. , Omodt H. W.
Published: July 2010

The macromorphology of several groups of well‐drained Chernozems in Eastern North Dakota that have developed in glacial till are described. A general map shows the areas where these soils occur and the location of sites sampled. Laboratory analyses of two profiles representative of each of three of these soil groups include: particle size distribution, pH, organic carbon, CaCO3 equivalent, clay size carbonates, free iron oxides, and the shale and chert content of the sand fractions.

The processes involved in the development of these soils from the glacial materials include: accumulation of organic matter and associated structure formation; redistribution of carbonates and more soluble salts; color changes; and formation of prismatic, finer textured B horizons primarily by alternate wetting and drying and weathering ‘in situ.’ Differences in the magnitude of these changes and in the original materials account for the Forman, Intermediate, and Barnes soils.
Trafficability of Four Loess Soils
Authors: Bassett J. R. , McDaniel A. R.
Published: July 2010

Strength of the 15‐ to 30‐cm layer of 65 modal sites on Loring, Grenada, Calloway, and Henry silt loams varied as much within series as between. Thus, little accuracy of strength prediction was lost by grouping the series for trafficability purposes. The group equation relating strength to moisture content accounted for 66% of the strength variation.
The Effect of Nonuniform Water Application on Soil Moisture Content, Moisture Depletion, and Irrigation Efficiency
Authors: Cohen O. P. , Bresler E.
Published: July 2010

Soil moisture measurements with a neutron probe indicated considerable non‐uniformity of moisture application in a citrus grove. Surface recharge was well correlated (r = 0.89) with interna recharge immediate'y after irrigation, but the coefficient of correlation decreased (r = 0.68) as the moisture was redistributed in the soil. Higher terminal moisture contents after irrigation, and higher rates of moisture depletion during the initial period of subsequent drying cycles, were measured in the soil volumes receiving higher rates of moisture application. Even though moisture application was nonuniform, irrigation efficiency was high, since the terminal moisture content was affected and the maximum wetting depth remained within the root zone. These effects of nonuniform moisture application must be considered during moisture requirement experiments if gross errors are to be avoided.
Ion Distribution, Moisture Content and Density of Soil Columns Measured with Gamma Radiation
Authors: Shalhevet J. , Yaron B.
Published: July 2010

Anion distribution in soil columns was measured nondestructively by using a radioactive tracer, 60Co (CN)63‐. The breakthrough curves of Cl‐ and 60Co (CN)63‐ were very similar, indicating the possible use of the 60Co complex ion as a qualitative model for anion movement. The external measurement of gamma activity was compared to measurements of 1:1 water extracts of the sectioned columns. The gamma activity of the tracer was measured along uniformly packed soil columns through a few drying and wetting cycles. Drying was done with a stream of warmed air that passed around and through the perforated soil columns. Moisture content and density of the soil in the columns were measured simultaneously by the gamma attenuation method. An equation, the parameters of which were determined empirically, giving density as a linear function of moisture content, may be introduced into the attenuation equation to correct for the variation of density with moisture content.
Characteristics of Ammonia Adsorption by Homo‐Ionic Clays
Authors: du Plessis M. C. F. , Kroontje Wybe
Published: July 2010

Adsorption of ammonia by aluminum‐saturated bentonite and kaolinite was described by Langmuir's adsorption equation. The inverse values of the slopes of the two straight line segments of each adsorption isotherm approximate the permanent charge and the total charge or cation exchange capacity at a particular pH (above 6), respectively.

Ammonia was presumably adsorbed as NH4+ to the full extent of the permanent charge and in addition ammonia appeared to be chemisorbed at pH‐dependent sites. Exchangeable Al3+ as well as hydroxy aluminum compounds may be precipitated as Al(OH)2 provided that the concentration of ammonia is high enough.

For homo‐ionic calcium, magnesium, sodium and potassium clays Langmuir's adsorption equation did not characterize chemisorption of ammonia from aqueous ammonia solutions satisfactorily. The S‐shaped ammonia adsorption isotherms obtained do not necessarily support the theory of physical multilayer adsorption.
Properties of the Available and the Soluble Molybdenum Fractions in a Raub Silt Loam
Authors: Follett R. F. , Barber S. A.
Published: July 2010

The available molybdenum (Mo) in a Raub silt loam, determined with the bioassay procedure using Aspergillus niger M., was 3% of the total Mo in the soil. Available Mo could be removed by daily displacement with water of the water held by the soil in a leaching column. Incubating the leached soil at room temperature and in a moist condition for 7 months following removal of the available Mo by leaching failed to cause an appreciable conversion of the Mo from the unavailable to the available form. The available Mo in the soil moved readily to the soluble form and at 4C and 26C followed a first‐order relationship.
Relation of Extractable Molybdenum to Soil Series and Parent Rock in Kentucky
Authors: Massey H. F. , Lowe R. H. , Bailey H. H.
Published: July 2010

Molybdenum extracted by the ammonium oxalate procedure proposed by Grigg was determined on 73 Kentucky soils. The Mo extracted by this method was related to the parent rock. Soils formed from Devonian black fissile shale contained approximately 20 times as much Mo as any other soil. Among the other soils the parent rock averages varied from 0.44 ppm Mo for older Ordovician limestone (generally high phosphatic) to 0.08 ppm Mo for Pennsylvanian sandstones and shales. The parent rock group differences were highly significant. Grigg‐extractable Mo and soil pH give some indication of Mo availability in the soil, and it is suggested that knowledge of the general level of Grigg‐extractable Mo in soils of a given parent rock group may allow useful prediction of Mo availability on these soils. The data provide some indication of a degree of uniformity within soil series. If further work supports this indication, a more accurate prediction based on soil series should be possible.
Redistribution of Nutrient Elements in Corn (Zea mays L.): I. N, P, K, Ca and Mg Redistribution in the Absence of Nutrient Accumulation after Silking
Authors: Kissel D. E. , Ragland J. L.
Published: July 2010

The redistribution of N, P, K, Ca, and Mg by corn from its vegetative parts to the developing ear was measured. This was accomplished by comparing a set of plants grown outdoors and harvested approximately 12 days after silking with a similar set of plants whose nutrient supply was cut off at the same time but which were allowed to grow to maturity. The increase in dry weight of ears between the first and second harvest was 174 g. The mean ear weight of the plants comprising the second harvest was 219 g.

Chemical analysis of the various plant parts permitted a measure of the losses and gains of mineral elements from the first to second harvests. Of the total present in all vegetative plant parts at harvest 1, the following percentages of the various plant nutrients had moved out of the vegetative parts by harvest 2: N, 65%; P, 76%; K, 23%; Ca, 0%; Mg, 45%: If all the plant nutrients redistributed from the vegetative parts between harvest 1 and 2 moved to the developing ear, the following percentages of the nutrients in the mature ear were supplied by the redistribution process: N, 97%; P, 116%; K, 180%; Ca, 0%; and Mg 133%.
Two‐Phase Experiments with Plants Growing in Phosphate‐Treated Soil
Authors: Matar A. E. , Paul J. L. , Jenny H.
Published: July 2010

Barley (Hordeum vulgare) and rye (Lolium multiflorum) plant were grown in phosphate‐treated soiland in an equilibrium nutrient solution which circulated continuously through soil potsand sand pots. The plants in soils always grew better and accumulated more phosphorus than the plants in sand. Plant physiological tests showed that the sand plants did not measureably deplete the circulating solution; therefore, the cause of this two‐phase effect must have resided in the soil.
Water Disposition in a Stream Channel with Riparian Vegetation
Authors: Qashu Hasan K. , Evans D. D.
Published: July 2010

Water losses along stream channels in the semiarid southwestern United States are of utmost importance when considering water disposition and water yields from a watershed. An analysis is described for estimating the disposition along a reach of a natural stream channel with a riparian vegetation and impermeable bedrock at a shallow depth. Results for one annual cycle are presented which indicate the quantity of water removed from the stream channel reach by various processes.

Methods were adapted for the particular set of conditions to measure subsurface water flow and water storage in the channel alluvium. Subsurface water flow was calculated from Darcy's equation. Water storage was estimated from water content, water table elevation, specific yield and volume of alluvium measurements.

Four distinct water‐use periods were apparent within a yearly cycle, each expressed by a separate water balance equation. Water losses by evapotranspiration were estimated from these equations. For example, 9 mm of water were estimated to be lost per day by transpiration of the riparian vegetation during the months of May and June, a time of water shortage in the area. Total depth of annual water loss by evapotranspiration from the channel reach was estimated to be 131 cm of water (4.3 acre‐feet/acre).
Soil Moisture and Soil Temperature Changes with the Use of Black Vapor‐Barrier Mulch and Their Influence on Pineapple (Ananas comosus (L.) Merr.) Growth in Hawaii
Authors: Ekern Paul C.
Published: July 2010

As the mulching practice in pineapple culture in Hawaii has developed over the last 50 years, a number of functions have been assigned to the action of the mulch. This study gives primary consideration to the effect of soil moisture and soil temperature changes upon pineapple growth. Soil moisture changes were determined from field samplings and lysimeter studies at Wahiawa, Oahu. Changes in the soil moisture budget with the mulch were so slight that the variability of field sampling precluded assessment without excessive replication. Coefficients of variability for samples taken at the plant butt were 3 to 5% of a moisture constant (e.g., 15‐bar point) for a soil series or within a single field. Moisture use, measured by semicontained hydraulic lysimeters, was reduced by the mulch when the soil was very wet but changed little when the soil moisture ranged from field capacity (0.15‐bar) to the 15‐bar point.

The mulch raised the average soil temperature about 1.6C during the winter. The measured one‐third increase in the plant growth was nearly identical with the increase calculated from the growth‐response of pineapple to temperature.
Differential Responses of Slash Pine Progeny Lines to Some Cultural Practices
Authors: Pritchett W. L. , Goddard R. E.
Published: July 2010

In three experiments involving intensities of management' slash pine (Pinus elliottii Engelm. var. elliottii) progenies of selected lines and crosses varied greatly in their growth rates on unaltered sites and in growth responses to environmental improvements. In three tests, some selections made poor growth in unfertilized soil, but responded well to fertilizer applications, while others made good growth in unfertilized soil, but were little affected by fertilizers. Of greater importance, some progeny lines made good growth in unfertilized soil and at the same time responded to fertilizer treatments.

There were greater growth differences within progeny lines due to variations in the immediate environment than there were among lines of different geographic origin.

These results emphasize the importance of testing progenies of plus trees on soils as productive and similarly managed as under plantation conditions.
Culture‐Table Air‐Ducts for Glasshouse Cooling
Authors: Reisenauer H. M. , Arkley T. H.
Published: July 2010

A modification of glasshouse culture tables into a cooled air distribution system is described. Conditioned air is passed upward around the pots and plants. This modification provides a uniform air temperature environment over the table surface, and, as compared to conventional systems, greatly reduces the maximum root media temperatures attained.
The Apparent Effect of Water Structure on K Uptake by Plants
Authors: Miller Raymond J. , Davey C. B.
Published: July 2010

The effect of temperature on K‐uptake by wheat seedlings was determined. Repressions in K‐uptake were found near 15 and 30C. These repressions correspond to changes (higher order phase transitions) in the structure of water and aqueous solutions.
Automated Particle‐Size Separation by Sedimentation
Authors: Rutledge E. M. , Wilding L. P. , Elfield M.
Published: July 2010

The fractionation equipment described is an automation of the common sedimentation‐decantation technique for particle‐size separation. It has the advantages of reducing the labor requirements and hastening completion of the separation.
Comparison of Water Content‐Pressure Head Data Obtained by Equilibrium, Steady‐State, and Unsteady‐State Methods
Authors: Topp G. C. , Klute A. , Peters D. B.
Published: July 2010

The water content‐pressure head relationship for a small, well‐confined, rectangular sample of fine sand was obtained under different water flow conditions. Water contents were measured by a gamma system and pressure heads were measured by a tensiometer‐pressure transducer combination. During drying, more water was retained in the sand at a given pressure head in the unsteady flow case than in the static equilibrium and steady‐state cases, which agreed with each other.
Potassium and Ammonium Fixation by Vermiculitic Soils
Authors: Page A. L. , Burge W. D. , Ganje T. J. , Garber M. J.
Published: July 2010

The fixation of potassium (K) and ammonium (NH4) against removal by unbuffered salts under wet and air‐ and oven‐dry (110C) conditions by vermiculitic soils is reported. Under wet conditions, the soils exhibited a rather definite capacity to fix NH4 and K; amounts of NH4 and K fixed were essentially equal. Exchange capacity reductions accompanying wet fixation demonstrated that an irreversible exchange adsorption mechanism would account for practically all of the NH4 and K fixed. The amount of NH4 and K fixed under air‐ or oven‐dry conditions was comparable to the amount fixed under wet conditions where the amount of NH4 and K added did not exceed the fixing capacity observed under wet conditions. However, when the amount added to soils to be subjected to oven drying exceeded the fixing capacity established for soils under wet conditions, NH4 and K were fixed without a further reduction in the cation exchange capacity, indicating the occurrence of a fixation process or processes not associated with the cation exchange capacity.
Clay Mineralogy and Mica‐Vermiculite Layer Charge Density Distribution in the Switzerland Soils of Indiana
Authors: Post Donald F. , White Joe L.
Published: July 2010

A study was made of the weathering of mica inherited from Ordovician limestone and calcareous shales in two (I and II) Switzerland soils, which belong to the Typic Normudalf, fine, mixed mesic family. X‐ray and physico‐chemical studies of the clay fraction showed that the solum of Switzerland I had an average of 24% mica and 35% vermiculite and the solum of Switzerland II was 40% mica and 24% vermiculite.

Layer charge density calculated from the ratio Σ(CEC + total K)/m2 clearly showed the decrease in charge density moving from the parent material upward in the soil profiles. The degree of swelling of the vermiculite on solvation was a function of this charge density. Magnesium‐saturated, glycerol‐solvated samples remained at 14.2A; Mg‐saturation and ethylene glycolation expanded some vermiculite to 16 to 16.5A; Ca‐saturated and glycerol treatment resulted in expansion of vermiculite to 17A; and K‐saturation and air drying readily collapsed most of the vermiculite to 10 to 10.3A.
Miscible Displacement of Nitrate through Soil Columns
Authors: Corey John C. , Nielsen Donald R. , Kirkham Don
Published: July 2010

One hundred milliliters of an aqueous solution containing 0.55 g of CaCl2 and 0.35 g of Ca(NO3)2 · 4H2O was displaced through 30‐cm long acrylic plastic columns containing soil. Velocity of water flow, sucrose concentration of the solution, and water content of the columns affected the loss of nitrate. Nitrate loss was determined by comparing breakthrough curves of nitrate with chloride. No nitrate was lost at a flow velocity of 1.32 cm/hr, but 21% was lost at 0.11 cm/hr. At a flow velocity of 0.11 cm/hr and sucrose concentrations of 0, 50, and 200 ppm, the losses of nitrate amounted to 21, 21, and 67%, respectively, of the total added. A net gain of nitrate was observed under unsaturated flow conditions.