bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Regime of a Prairie Snowcover
Authors: Granger R. J. , Chanasyk D. S. , Male D. H. , Norum D. I.
Published: July 2010

An energy budget approach was used to study the melting of a shallow prairie snowpack. In the analysis, all the terms of the energy budget were determined independently. The major source of energy for the melt was the net radiation flux. Over a continuous snowcover the contribution of sensible heat to the melt could not be represented by a simple low‐level temperature index, but was dependent on the energy content of the air mass. The latent heat flux responded to the radiation flux, with daytime evaporation and nighttime condensation, however the net daily flux was evaporative. Nighttime refreezing of the snowpack limited the runoff, with approximately 40% of the daily meltwater being retained or refrozen in the snowpack. Beneath the melting snowcover the diurnal cycle of soil heat flux was almost completely eliminated. Monitoring of soil moisture changes during the melt period showed that very little infiltration occurred until the soil had thawed.
Dissolution of Arsenic from Waterlogged and Aerated Soil
Authors: Hess R. E. , Blanchar R. W.
Published: July 2010

Sharpsburg and Menfro soils containing 320 and 160 µg As/g, respectively, were waterlogged with water or 1% dextrose. The Eh reached a minimum of −150 mV after 1 day of incubation and increased to about +300 mV after 12 days for both soils in 1% dextrose. The Eh remained constant in the Sharpsburg soil during incubation with water, but gradually decreased in the Menfro soil. In the 1% dextrose solution, As increased rapidly in both soils and became constant after 12 days. The As in solution increased more slowly when incubated with water, but also remained constant after 12 days. After freeze‐drying and exposing the soil to the atmosphere, Eh increased and As decreased to initial levels.

The values of pAl + 3pOH, pAl + pAsO4, pFe + 3pOH, pFe + pAsO4, 3pMn + 2pAsO4, 3pCa + 2pAsO4, and 3pPb + 2pAsO4 were computed. These measurements indicated that the soil solution of the Menfro and Sharpsburg soils contained less As than predicted for Al, Fe, and Ca arsenates, and more As than predicted for Mn and Pb arsenates.
Homovalent and Heterovalent Cation Exchange Equilibria in Soils with Variable Surface Charge
Authors: Galindo G. G. , Bingham F. T.
Published: July 2010

Cation‐exchange equilibira involving K, Na, Ca, and Mg were studied with Chilean Dystrandepts.

The K‐Na exchange and the Ca‐Mg exchange showed that K and Ca were preferentially adsorbed. Increased charge density through adsorption of phosphate resulted in a reduction in the selectivity for K in the K‐Na system. Phosphate adsorption had no apparent effect on the selectivity for Ca in the Ca‐Mg system.

In heterovalent systems, these soils showed a perferential adsorption of the divalent cation. This selectivity was more pronounced at low equivalent concentration of the divalent cation. The selectivity for the divalent cation increased as the surface charge density was increased by phosphate adsorption.
Characteristics of Coatings formed on Rice Roots as Affected by Iron and Manganese Additions
Authors: Bacha R. E. , Hossner L. R.
Published: July 2010

Rice plants (Oryza sativa ‘Brazos’) were grown with varying rates of application of Fe and Mn. Solution concentration of Fe ranged from 0.5 to 50.5 ppm and Mn from 0.1 to 12.5 ppm in an experiment designed to study the coatings formed on rice roots grown under anaerobic conditions. Root coatings were removed for analysis with citrate‐bicarbonate‐dithionite solution. Chemical analysis inidcated that the coatings were composed primarily of Fe. Manganese was present in detectable amounts only when solution concentrations were > 1.0 ppm.

Scanning electron micrographs of the coatings showed a precipitate on the surface of the rice root. X‐ray diffraction analysis of coatings identified the iron oxide mineral lepidocrocite (γ‐FeOOH) as the only crystalline component of the coatings.
Adsorption of Aluminum by a Smectite: II. An Al3+‐Ca2+ Exchange Model
Authors: McBride M. B. , Bloom P. R.
Published: July 2010

The adsorption of Al by Ca2+‐montmorillonite has been found to be described by a Langmuir‐type equation in which the activity of Al3+ in solution is a function of the coverage of the mineral surfaces by Al. The classical mass‐action equations were inadequate in describing the exchange reaction where the Ca2+ activity was allowed to vary, weighting the effect of the Ca2+ ion activity on the equilibrium too heavily. The model suggests the relative solutionlike nature of adsorbed Ca2+ compared to the much more strongly adsorbed Al3+. Hydrolysis and precipitation reactions of Al3+ at higher pH complicated the exchange model by introducing significant quantities of adsorbed hydroxyl‐Al into the system.
Characteristics of Some Selected Soils in the Caspian Sea Region of Iran
Authors: Hakimian M.
Published: July 2010

A physiographic sequence of soils was studied in the Caspian Sea region of Iran. This area is characterized by a warm, temperate, humid microclimate. Seven representative pedons, including 34 samples, were analyzed.

Physico‐chemical determinations revealed that the Mountain and Upper Alluvial Plain soils are acid with average pH values of 5.8 and 5.9, respectively. The Lower Alluvial and Coastal Plain soils are neutral with pH's of 7.0 and 7.3, respectively. The base saturation percentages are lower for highland soils (68% for Upper Alluvial Plain area) and higher for lowland soils (99% for Coastal Plain area). The exchange acidity also follows the reverse trend. The average organic matter content of the Lower Alluvial Plain soils is the highest (9%) among the soils studied, while that of the Upper Alluvial Plain soils is lowest (2.3%). The other soils have intermediate OM content, being variable throughout the pedons 1, 3 and 7. The Mountain soil exhibits the highest CEC value (41.6 meq/100 g), while the other soils have considerably lower values. However, the average vermiculite content of the Mountain soil is lower (20%) than those of the plains (ranging from 34 to 43.8%). Clay mica content of the soils also follows the same general trend.

X‐ray diffraction patterns of the clay fractions reveal that the dominant clay minerals consist of kaolinite, randomly interstratified montmorillonite‐vermiculite, and some discrete vermiculite. The clay mica (illite) is more common in the soils of the plains, while discrete chlorite as well as clay mica‐chlorite and/or vermiculite are observed in the clay fraction of the low‐land soils.

The soils are classified as follows: Mountain soil as Typic Hapludoll; Upper Alluvial Plain soils as Aquic Hapludalf, Fluventic Eutrochrept, and Dystric Fluventic Eutrochrept; Lower Alluvial Plain soils as Aeric Haplaquept; and the Coastal Plain soil as Fluventic Hapludoll.
Soil Development as a Function of Time in The Punjab River Plains of Pakistan
Authors: Ahmad M. , Ryan J. , Paeth R. C.
Published: July 2010

Three soil series; Shahdara (Ustifluent), Sultanpur, (Ustochrept) and Bhalwal (Haplustalf), representing a chronosequence from the Punjab River plains of Pakistan, were studied with respect to morphological, chemical, physical, and mineralogical properties. These soils, developed in mixed mineral alluvium, represented the late Holocene, middle Holocene, and late Pleistocene surfaces and were estimated to be less than 100 years, around 2,300 years, and between 10,000 and 20,000 years old respectively. With increasing soil age, horizon differentiation and solum thickness increased while cutans and CaCO3 concretions occurred in the oldest Bhalwal soil. Topsoil CEC and TEB values increased while both CaCO3 content and the Ca:Mg ratio decreased. Significant changes occurred in the ratio of acid oxalate to citrate‐dithionite extractable iron (Fe ratio). Textural gradation was in evidence in the two older soils. Illite and chlorite tended to decrease, and vermiculite and montmorillonite to increase with soil age. Despite variability in parent materials due to depositional stratification and preweathering, the changes in soil properties with age were mainly attributed to processes of soil formation.
Mineralogy of Soils Developed on Alluvium in the Indo‐Gangetic Plain (India)
Authors: Sidhu P. S. , Gilkes R. J.
Published: July 2010

X‐ray diffraction, electron microscopic, and petrographic techniques have been employed to study the mineralogy of four soils developed on the Indo‐Gangetic alluvium in northwestern India. Sand and silt fractions are dominated by primary quartz. Other minerals present in these fractions include muscovite, plagioclase and alkali feldspars, amphibole, biotite, and chlorite. Illite, chlorite, and kaolinite have been identified in the clay fraction of each soil with smectite being present in one soil. Both muscovite and illite belong to the dioctahedral 2M1 polymorph, whereas chlorite is trioctahedral. Quartz and feldspar grains appear to be unaltered and very angular. Although the studied soils show morphological and physico‐chemical evidence of pedogenesis, mineral alteration has been minimal. The mineralogy of all the soils is very similar and no changes in the mineralogical make‐up with depth in a particular pedon have been observed. Soil mineralogy can be related to the mineralogy of rocks in the source areas which contributed sediments. It is considered that insignificant post depositional weathering of sediments has occurred.
Estimation of the Spatial Variability of the Soil‐Water Flux
Authors: Rao P. S. C. , Rao P. V. , Davidson J. M.
Published: July 2010

A simple method for estimating the spatial variability of the soil‐water flux from known variability of soil microhydrologic properties is presented. The method is based on the theory of approximating a differentiable function using Taylor‐series expansion (TS‐method). Published data for means and variances of the soil microhydrologic properties were used to estimate the mean and variance of the soil‐water flux in a draining profile of Panoche soil. These values were compared with those estimated using a Monte Carlo simulation procedure (MC‐method) on the same set of data. Relative advantages and disadvantages of these two methods are briefly discussed.
The Lithoplinthic Horizon, a Diagnostic Horizon for Soil Taxonomy
Authors: Smith Guy D. , A. Pedro Brito , Luque Oswaldo
Published: July 2010

A new diagnostic horizon, the lithoplinthic horizon, is proposed for an indurated ironstone that contains many irregular, tubular, channels filled with fine earth, that conduct water and permit plant roots to reach underlying horizons. It is hard rock for many engineering interpretations and soil for interpretations for plant growth. It is proposed that, if there are no overlying diagnostic horizons other than an ochric epipedon, the soils should be classified as lithoplinthic subgroups of Orthents. Use of family classes of particle size and depth is proposed, but not of mineralogy.
The Mechanism of Sulfate Adsorption on Iron Oxides
Authors: Parfitt Roger L. , Smart Roger St. C.
Published: July 2010

Adsorption isotherms were determined for sulfate adsorption on iron oxides under acid conditions. The product of the surface reaction between the iron oxides and sulfate ions was examined by infrared spectroscopy which showed four bands in the v S‐O stretching region. Thus a structural model could be obtained for the reaction. Two surface hydroxyl groups (or OH2+ ions) are replaced by one sulfate ion, and two oxygen atoms of the sulfate ion are coordinated each to a different Fe3+ ion, resulting in the binuclear bridging surface complex Fe‐O‐S(O2)‐O‐Fe. The complex is formed on the surfaces of goethite (α‐FeOOH), akaganéite (β‐FeOOH), lepidocrocite (γ‐FeOOH), hematite (α‐Fe2O3) and amorphous ferric hydroxide.
A Study of a Deep Weathering Profile on Granite in Peninsular Malaysia: III. Alteration of Feldspars
Authors: Eswaran H. , Bin Wong Chaw
Published: July 2010

Feldspar grains or their pseudomorphs from the different weathering zones are studied with the SEM. Weathering commences with dissolution to form voids in the grains. Close to the rock, the first product is allophanic material present as globules adhering to the voids in the grains. In the δ zone the product is halloysite with some amorphous silica spherules. The surface of the pseudomorph has a hummocky appearance suggesting an amorphous intermediary phase prior to halloysite formation. Kaolinite formation commences in the γp zone and gibbsite in the γm zone. Admixtures of kaolinite and halloysite may be found on the same pseudomorph, but admixture of gibbsite with another secondary mineral is not encountered.

Biotite follows a similar trend of alteration. It is concluded that irrespective of the primary weatherable mineral, the type of secondary mineral found is a function of the microenvironment.
Interaction of Monomeric Silicic Acid With Copper and Zinc and Chemical Changes of the Precipitates With Aging
Authors: Leggett G. E.
Published: July 2010

Precipitates were formed by titrating dilute, acidic solutions of monomeric silicic acid [Si(OH)4] and copper (Cu) or zinc (Zn) to various pH values. Those containing Cu formed above pH 6.0; those containing Zn formed above pH 7.0. Periodically, during 2 years of aging in their mother liquor, the liquid phase was sampled and analyzed and the Cu/Si or Zn/Si molar ratios of the precipitates calculated. The Cu/Si ratios of those containing Cu stabilized readily near 0.78 and were unaffected by pH. The Zn/Si ratios of the Zn‐containing precipitates, however, changed as a result of Si enrichment from near 1.80 soon after their formation to near 0.80 after aging 2 years. The systems with the lowest pH changed first and most rapidly and became stabilized within 6 months; those above pH 8.0 changed more slowly.

The Zn‐containing precipitates gave diffuse X‐ray diffraction patterns indicative of a 2:1 layer silicate, whereas those containing Cu were amorphous.
Scanning Electron Microscopy of Rhizobium spp. Adhering to Fine Silt Particles
Authors: Fehrmann R. C. , Weaver R. W.
Published: July 2010

Bacterial polysaccharides binding to soil particles were observed with the scanning electron microscope. The bacteria were grown in shake culture with dispersed silt particles (2–5 µm) to promote polysaccharide‐soil particle interactions. Species of Rhizobium were used because of their abundant polysaccharide production. The mucilagenous polysaccharides exhibited connective networks that joined particles to one another and also to bacteria. Aggregates of particles were seen only when bacterial polysaccharides were present. These micrographs provide visual evidence of the binding action of bacterial polysaccharides to soil particles.
Approximate Analytical Solution for Solute Flow During Infiltration and Redistribution
Authors: De Smedt F. , Wierenga P. J.
Published: July 2010

An approximate analytical solution is developed to describe solute flow in soil during infiltration and redistribution. For the solution it is assumed that hydrodynamic dispersion is linearly related to the pore water velocity. In order to use the solution it is necessary to estimate the solute penetration depth. Methods of estimating the solute penetration depth are discussed. Solute concentration distributions computed with the approximate analytical solution are compared with those obtained with a numerical model. It is shown that the solution proposed is most useful during the infiltration phase. During the redistribution phase the approximate analytical solution provides a first‐order estimate of the solute distribution with time and depth. Computed chloride distributions compare favorably with chloride concentrations observed by Warrick et al. (1971).
Root Growth in Cores Formed from Fragipan and B2 Horizons of Hobson Soil
Authors: Blanchar R. W. , Edmonds C. R. , Bradford J. M.
Published: July 2010

The effect of changes in acidity and bulk density of cores formed from B2 and fragipan horizons of a Hobson soil on probe penetration and pea root growth were evaluated. Increasing soil pH in the range of 4.2–6.5 had no measurable effect on probe resistance, but resulted in greater root length in both B2 and fragipan samples. Probe penetration resistance increased as bulk density was increased. The silty clay loam B2 horizon was more resistant to probe penetration than the sandy loam fragipan when compared at the same bulk density and moisture tension. Root length was more closely related to probe penetration resistance than to bulk density. Root growth in both B2 and fragipan soil decreased as probe resistance increased from 10 to 20 bars and essentially stopped in soil where probe penetration resistance exceeded 20 bars.
Spatial Variation of Sand Content and pH Within Single Contiguous Delineations of Two Soil Mapping Units
Authors: Campbell James B.
Published: July 2010

Quantitative estimates were made of the rates of spatial variation of soil properties within each of two sampled areas displaying contrasting patterns of variation. Samples were collected at 10‐m intervals on two sampling grids, each 8 by 20, positioned on contiguous delineations of the Ladysmith and Pawnee series in eastern Kansas. The Pawnee is developed from glacial till, the Ladysmith from fine‐textured sediments.

Spatial variation of sand and pH measurements within both of the sampled areas was studied using the semivariance, a statistical function tailored for the analysis of continuous geographic variables. There is a contrast in spatial variation of sand content within the two areas; in the Ladysmith area, a distance of 30 m is sufficient to encounter full variation of sand content, but in the Pawnee area, a distance of 40 m is required. pH has random variation within both areas. This information can be used to select optimum spacing of samples in designing soil sampling plans.
Effect of Mulching on Sediment in Runoff From Simulated Rainfall
Authors: Singer Michael J. , Blackard John
Published: July 2010

Simulated rainfall was used to test the relationship between sediment in runoff and percent of the soil that was mulch covered. Oak leaves (Quercus Douglasii H. & A.), redwood litter (Sequoia sempervirens (D. Don) Endl.) and oat straw (Avena barbata Brot.) were used as mulches on a 0.37m2 plot of Auburn (loamy, mixed, thermic, Ruptic‐Lithic Xerochrepts) surface soil at a 9% slope. Cover percentage was related to sediment in surface runoff by a parabolic relationship. The relationship between redwood and oak covers and sediment in runoff was not significantly different, but both were significantly different from oat straw. Cover shape or distribution of inter‐cover space appears to be important in affecting sediment loss. Runoff volume was significantly reduced by high cover levels which protected the soil from sealing and helped maintain a high infiltration rate.
Solubility Product of Belle Fourche and Colony Montmorillonites in Acid Aqueous Solutions
Authors: Kittrick J. A.
Published: July 2010

Published solubility studies for Belle Fourche and Colony montmorillonites were re‐examined to help answer the question as to whether or not montmorillonite can come to equilibrium with acid aqueous solutions. Values of pH‐⅓pAl3+ for both montmorillonites were plotted against pH4SiO4 after adjusting to common values of pH‐½pMg2+ and pH. Three lines of reasoning indicate that selected Belle Fourche montmorillonite samples came to equilibrium with acid aqueous solutions during a 3‐to‐4‐year study period. First, the slope of the solubility line for Belle Fourche montmorillonite was in agreement with that predicted for equilibrium with a solid phase of the same Al/Sl ratio as Belle Fourche montmorillonite. Second, the stability of the solubility line in relation to the stability of other minerals agreed with known natural relationships, and third, the precision of the pK values is well within experimental error. Similarly adjusted pH‐⅓pAl3+ values for Colony montmorillonite have a wide scatter when plotted against pH4SiO4. This scatter indicates that collectively these samples had not come to equilibrium with any solid phase during a study period of approximately 1 year or less. By examining comparable data for gibbsite (previously unpublished) it is shown that variation in the apparent pK values for Colony montmorillonite may be a consequence of pH variation as the system approaches equilibrium. It is argued that statistical relationships between nonequilibrium components for noncongruent dissolution do not permit conclusions with regard to equilibrium relationships for either Colony montmorillonite in particular, or solid phases in general.
Copper and Cadmium Adsorption Characteristics of Selected Acid and Calcareous Soils
Authors: Cavallaro N. , McBride M. B.
Published: July 2010

Samples of two New York soils, an acid and a neutral silt loam, were equilibrated with Cu2+ and Cd2+ solutions in concentrations ranging from 10−5 to 10−4M in distilled water and in 0.01M CaCl2. The extent of complexation and adsorption of the heavy metals was measured using specific ion electrodes and atomic absorption. The data were found to fit the Langmuir adsorption model, and the Cu2+ adsorption maxima were greater than those of Cd2+ for both soils. Acid soils demonstrated much less ability to retain the heavy metals than neutral soils. In the presence of 0.01M CaCl2, adsorption of the metals was much reduced, suggesting Ca2+ competition for adsorption sites. A considerable amount of Cu2+ was complexed in the soil solutions, but Cd2+ complexation was much less evident. The results support an ion exchange mechanism of adsorption in the surface soils, and suggest that precipitation occurs in calcareous subsoils.
A Chemical and Spectroscopic Characterization of some Synthetic Analogues of Humic Acids
Authors: Mathur S. P. , Schnitzer M.
Published: July 2010

Fourteen analogues of humic acids (“HA's”) were synthesized from phenols, quinones, and salicylic acid by methods described in the literature. Elemental and functional group measurements, and infrared and electron spin resonance spectroscopy, indicated that seven of these “HA's” were in general similar to natural HA's. These “HA's” were methylated and further investigated by chemical degradation. Identities and quantities of the methylated degradation products resembled those from natural HA's treated in the same way. Thus, “HA's” resulting from oxidative polymerizations of salicylic acid, catechol, hydroquinone, and pyrogallol, under a variety of reaction conditions, appear to be suitable for investigations of interactions of humic materials with pesticides, enzymes and other N‐compounds. Some of these synthetic “HA's” can be readily prepared in any laboratory and, in contrast to microbially‐synthesized “HA's”, also as N‐free analogues.
Analytical Properties of the Soluble, Metal‐complexing Fractions in Sludge‐soil Mixtures: III. Unaltered Anionic Surfactants in Fulvic Acid
Authors: Holtzclaw Kenneth M. , Sposito Garrison
Published: July 2010

A rapid analytical procedure was developed for the quantitative determination of unbiodegraded anionic surfactants in the fulvic acid fraction of sewage sludge. This procedure, which is a modification of the methyl green method of Moore and K olbeson, consists of: (i) hydrolysis in 4N HCl, (ii) separation on an anion exchange resin, (iii) extraction of a methyl green‐surfactant complex into benzene, and (iv) colorimetric determination of the complex. The modified procedure is free of the negative interferences that occurred when the original methyl green method was applied to a sludge‐derived fulvic acid and does not require specialized reagents or expensive instrumentation.

An application of the modified procedure to two representative fulvic acids extracted from anaerobically‐digested sewage sludges indicated that about 5% of the dry mass of a sludge‐derived fulvic acid (water‐ and ash‐free basis) may be attributed to unaltered anionic surfactant compounds. This result suggests that a significant aspect of the chemistry of agricultural soils into which sewage sludge has been incorporated will be reactions involving both unaltered and partially biodegraded anionic surfactants.
Tillage Implements − Soil Structure Relationships and Their Effects on Crop Stands
Authors: Hadas A. , Wolf D. , Meirson I.
Published: July 2010

Under rainfed dryland farming, tillage performed on a dry soil prior to the rainy season is the most important practice to improve the soil physical conditions for crop establishment and development. However, questions have seldom been raised as to the degree of clod breakdown required to improve soil physical conditions for seed germination, as well as the cost in energy and number of implements involved.

The objectives of the work reported here were to: (i) collect and correlate data concerning energy input with the degree of soil clod breakdown and aggregate size distributions attained by various tillage implements and operation sequences when performed on dry soils; and (ii) to compare crop stands under field conditions on differently tilled plots.

Crop stands and fineness of seedbed tilth were not significantly correlated. Yet, finer tilth could only be obtained through an elaborate tillage operation sequence and a tremendous input of energy if performed on air dry soils, whereas tilling the same soil while moist (approximately at wilting point‐moisture content), produced finer tilth at a much lower energy input.
Differential Infrared Spectroscopy in the Study of Parathion‐Bentonite Complexes
Authors: Mingelgrin U. , Yariv S. , Saltzman Sarina
Published: July 2010

Differential infrared spectroscopy was used to investigate parathion degradation in the adsorbed state. This technique enables observations of the 1,380–1,150 cm−1 region, which is usually overlapping with the strong SiO absorption of bentonites. The appearance of the P=O absorption band upon heating clay‐parathion complexes, in conjunction with other tests, confirmed that parathion degradation on bentonites occurs mainly via a rearrangement reaction.
Displacement of Soil Water by Simulated Rainfall
Authors: Quisenberry V. L. , Phillips R. E.
Published: July 2010

Displacement of initial soil water by simulated rainfall was measured in aggregates of Maury silt loam soil in columns in the laboratory and under field conditions using tritiated water and/or Cl‐ as a tracer of added water. Displacement values measured in aggregates were larger (53 to 85%) than those measured under field conditions (7 to 56%). Percent displacement of initial soil water in Calloway silt loam under field conditions were similar to those of Maury, but were larger in Huntington silty clay loam than in Maury. Initial soil water content of Maury soil did not appear to affect percent displacement. Percent displacement in Maury soil increased as the depth of tillage increased.
Electron Probe Microanalysis of Calcite Grains Containing Phosphorus in Soil
Authors: Qureshi R. H. , Jenkins D. A.
Published: July 2010

Calcite, comprising both clastic sand‐sized grains and fossil foraminifera inherited from a marine Cretaceous (“Gault”) clay, has been isolated from a haplaquept (“gleyic brown calcareous earth”) in the United Kingdom and shown by wet chemical analysis to contain an average of 0.3% phosphorus. Electron probe microanalysis indicates that this phosphorus is uniformly distributed within the calcite rather than concentrated as discrete calcium phosphates, and it is concluded that it was biogenic/diagenic rather than pedogenic in origin. Such sources constitute 50–80% of the total soil phosphorus and would be relatively available in the upper horizons of the profile.
Transport of a Noncohesive Sandy Mixture in Rainfall and Runoff Experiments
Authors: Walker P. H. , Kinnell P. I. A. , Green Patricia
Published: July 2010

Rainfall intensities of 45, 100, and 150 mm/hr with systematically varied kinetic energies were applied to a saturated noncohesive, sandy bed 3 m long and set at slopes of 0.5 and 5%. Detailed size analyses of solids discharged showed that the <31‐µm fraction was most readily mobilized and behaved as a suspended load; the 31‐ to 250‐µm fraction was transported slowly, much apparently as saltating bed load; the 0.25‐ to 4‐mm fraction was transported rapidly, grains tending to move as rolling bed load; the >4‐mm fraction behaved as a lag gravel. The sedimentary properties of bed deposits also reflected the differentiation of various size fractions and minerals in the original mixture. The effects of raindrop impacts within the flow were more important in promoting transport of solids than the aerial component of splash. Under conditions where overland flow had developed, transport of solids was related directly to rainfall intensity and variations in rainfall energy that were associated with variations in raindrop impact frequency. Increases in rainfall energy due to increasing raindrop sizes did not result in increases in solids discharged.
Iron Oxide Mineralogy of Well‐drained Ultisols and Oxisols: II. Influence on Color, Surface Area, and Phosphate Retention
Authors: Bigham J. M. , Golden D. C. , Buol S. W. , Weed S. B. , Bowen L. H.
Published: July 2010

Subsoil samples from selected North Carolina Ultisols and Brazilian Oxisols were analyzed to determine how the colors of these materials were influenced by the nature and distribution of their constituent iron oxides. The effects of extraneous variables, i.e., other than the iron oxides, were minimized by utilizing pairs of red and yellow soils that were otherwise similar in their physical, morphological, and mineralogical properties.

The iron oxides were found to be concentrated in the <0.2‐µm fractions, and the colors of these clays were the same as or similar to those of the parent soils. The spectral properties of the <0.2‐µm clays were primarily influenced by iron mineralogy. Goethite or mixtures of goethite and hematite were identified in all of the clays; however, Mössbauer analyses indicated that the red members of all sample pairs contained larger proportions of hematite than did their yellow counterparts. In addition, as the clays became redder in hue, the ratio of hematite to goethite generally increased. Calculated surface areas for the iron oxides ranged from 60 to 200 m2/g; values from the yellow clays were consistently higher than those obtained from their red counterparts. The yellow clays were also more efficient adsorbers of phosphate.
A Glass Filter Soil Solution Sampler
Authors: Long F. Leslie
Published: July 2010

An improved soil solution sampler utilizes a fritted glass tubular filter and does not alter the ionic concentration of the soil solution as do ceramic porous cups. The sampler is easy to build, install, and operate to characterize in situ soil chemical environment with time.
Phosphorus Supplying Capacities of Previously Heavily Fertilized Soils
Authors: Novais Roberto , Kamprath E. J.
Published: July 2010

Four Coastal Plain soils and one Piedmont soil heavily fertilized in the past were intensively cropped in greenhouse pots to determine changes in extractable soil P as measured by North Carolina, Bray I and Olsen extractants. Slopes relating changes in extractable P with P removed by cropping were very similar for the three sandy soils. Changes in extractable P with the North Carolina and Bray I extractants were correlated with P buffer capacity, % clay, and soil surface area. The principal source of P removed by cropping was NH4F‐P in sandy Coastal Plain soils; NH4F‐P and NaOH‐P supplied equal amounts in the clayey Piedmont soil. Sandy Coastal Plain soils which originally contained more than 74 ppm North Carolina extractable P and 71 ppm Bray I extractable P supplied 82 to 108 kg P/ha to nine crops of pearl millet (Pennisetum americanum, cv. Gahi‐1).
Effect of Winter and Summer Windbreaks on Soil Water Gain and Spring Wheat Yield
Authors: Frank A. B. , Willis W. O.
Published: July 2010

Field windbreaks have been planted primarily for soil erosion control, but they also affect the growth and yield of nearby crops by modifying the crop's microclimate (summer effects) or by trapping snow for soil water gain (winter effects). The purpose of this study was to partition and determine the summer and winter effects of noncompetitive windbreaks using ‘Waldron’ spring wheat (Triticum aestivum L.) as a test crop.

We erected 2.3‐m high by 32‐m long slat‐fence barriers in an eastwest direction during winter (W+S‐), summer (W‐S+), both winter and summer (W+S+), or not at all (W‐S‐). The top and bottom halves of each barrier were 42 and 21% dense, respectively. Three years of the 6‐year study were classified as wet years and three were dry years based on total available water (available soil water at seeding plus seeding‐to‐harvest precipitation) for the crop. Snow depth, soil water gain over winter, crop water use, wheat yield, and plant height were measured at 2H (H = barrier height) units to 6H north and 10H south of the barriers. Snow trapped by the barriers ranged from 1.2 m deep 5H south of the barrier in 1975 to no measurable snow in 1973. Soil‐water gain from snowmelt was greatest 5H south of the barrier and averaged 1.9 cm more over the test area for W+S+ and W+S‐ as compared with W‐S+ and W‐S‐ treatments. Average wheat yields for the 3 wet years were the same for all treatments, but for the 3 dry years the W+S+ and W+S‐ treatments increased yields by 3.2 and 2.1 quintal/ha, respectively, as compared with the W‐S‐ treatment. The summer‐only barrier (W‐S+) had no measurable effect on wheat yields. Wheat yields during the dry years were maximum at 5H south of the barrier, which coincided with maximum snow depths and overwinter soil water gains.

Results of this study showed that grain yield increases obtained adjacent to noncompetitive barriers were mostly due to increased overwinter soil water accretion resulting from snow catch (winter effects) and not microclimate modification (summer effects).
Influence of Row Spacing of Grain Sorghum on Ground Cover, Runoff, and Erosion
Authors: Adams J. E. , Richardson C. W. , Burnett E.
Published: July 2010

A study was begun at Temple, Texas, in 1972 to assess the effect of narrow (50‐cm) and conventional (100‐cm) row spacing of grain sorghum [Sorghum bicolor (L.) Moench] on runoff and erosion from field‐sized areas. Sorghum in narrow rows established a more complete plant canopy earlier than sorghum with conventional row spacing and provided more ground cover for much of the growing season. In 1973, runoff was 45% less and soil loss was 39% less from narrow‐row grain sorghum than from sorghum with conventional row spacing. Narrow‐row spacing of sorghum increased ground cover significantly (5% level) 35 days after emergence in 1974. Canopy cover was at maximum by 63 days after seedling emergence and provided a ground cover of 46 and 81% for sorghum with 100‐ and 50‐cm row spacing, respectively.
Nutrient Flux in Litter and Surface Soil after Nitrogen and Phosphorus Fertilization
Authors: Kelly J. M. , Henderson G. S.
Published: July 2010

The effect of urea and concentrated superphosphate additions on the movement of N, P, K, and Ca from the litter and top 10 cm of the mineral soil via the soil solution was evaluated in an upland oak forest using tension lysimeters. The range in total flux values for each element over the study period were: N 24.8 to 1145.3; P 2.0 to 633.3; Ca 70.6 to 553.1; and K 49.5 to 94.0 kg/ha in response to various combinations of N and P fertilizer addition at levels of 0, 550, and 1100 kg/ha N and 0, 275, and 550 kg/ha P. Nitrogen fertilizer addition significantly increased the flux of N and K while reducing the flux of P and Ca. Phosphorus fertilizer addition significantly increased N, P Ca, and K fluxes. Solubilization of organic matter and the formation of insoluble calcium ammonium phosphate were important processes regulating the flux of N, P, Ca and K.
Evaluation of Conceptual Models for Describing Nonequilibrium Adsorption‐Desorption of Pesticides During Steady‐flow in Soils
Authors: Rao P. S. C. , Davidson J. M. , Jessup R. E. , Selim H. M.
Published: July 2010

Breakthrough curves (BTC) from miscible displacement of two pesticides through three soils were measured for two input concentrations of each pesticide. These BTC data were used to evaluate two conceptual models for describing the nonequilibrium adsorption‐desorption of pesticides in soils under steady‐state water flow conditions. In both models, adsorption on one group of sites was assumed to be instantaneous, while the rate of adsorption on the second group of sites followed either nonlinear reversible kinetics (Model I) or was a diffusion‐controlled process (Model II). Parameters in both models were estimated by curve‐fitting model predictions to one set of measured BTC data using a nonlinear least‐squares optimization procedure. These parameter values were then used to verify the conceptual models by comparing simulated and measured BTC for a different input concentration. A different set of model parameters were required to describe the BTC data for each input concentration for the same soil‐pesticide combination. The measured 3H2O BTC for all three soils were symmetrical in shape with no apparent tailing. Evaluation of Model I and II using these BTC suggested that the mobile‐immobile water concept may not be applicable to the three soils used in this study.
Reactions of Ammonium Ortho‐ and Polyphosphate Fertilizers in Soil: II. Hydrolysis and Reactions with Soil
Authors: Khasawneh F. E. , Hashimoto I. , Sample E. C.
Published: July 2010

Reactions of P from triammonium pyrophosphate (TPP), ammonium polyphosphate (APP), and diammonium phosphate (DAP) were investigated in replicated columns of Hartsells fsl soil (a Typic Hapludult) at a moisture content of 19% that were incubated for 1, 2, or 4 weeks at 25°C. The diffusive movement of P was accompanied by two major reactions: (i) hydrolysis of pyro‐ and polyphosphates to the orthophosphate form; and (ii) precipitation reaction of all phosphatic anions with soil. Hydrolysis of the water‐soluble fraction of the condensed forms of P was rapid, with a half life that ranged from 9 to 16 days. Hydrolysis of the water‐insoluble fractions was severely retarded by their insolubility and could not be measured in 4 weeks. Because the rate of hydrolysis was faster than that of diffusion, mobility of the pyro‐ and polphosphates occurred largely in the orthophophate form and accounted for the similarity of P movement among the three sources. The precipitation reactions of pyro‐ and polyphosphate were virtually complete in the 1st week, were irreversible and localized within well‐defined zones, and accounted for nearly one‐fourth of the added P. Precipitation of orthophosphates increased considerably with time and higher concentrations of water‐soluble orthophosphate, and decreased by pyro‐ and polyphosphate competing for the same precipitating agents. Furthermore, orthosphate precipitation was dispersed rather than localized and showed signs of reversibility. The total water‐insoluble fractions after 4 weeks accounted for 58, 63, and 45% of added P from TPP, APP, and DAP, respectively.
Use of Inductively‐coupled Plasma Spectrometry for the Simultaneous Determination of Macro‐ and Micronutrients in NH4HCO3‐DTPA Extracts of Soils
Authors: Soltanpour P. N. , Workman S. M. , Schwab A. P.
Published: July 2010

Twenty‐six soils were extracted with 1M NH4HCO3‐. 0.005M DTPA solution (Soltanpour and Schwab, 1977). Inductively‐coupled plasma optical emission spectrometry (ICP‐OES) was used to simultaneously determine P, K, Zn, Fe, Cu, and Mn in the extracts. These analytical results were compared with those obtained with a colorimetric method for P and flame atomic absorption spectrometry (AAS) for the cations. It was necessary to change the carbonate‐bicarbonate matrix (1M) to a more soluble matrix in order to prevent formation of crystals and clogging at the capillary tip. This was achieved by a 1:5 dilution with 0.5N HNO3 followed by shaking for 10 min. Results from the ICP‐OES and the flame AAS methods were comparable. Analysis of P by ICP‐OES gave larger values than analysis by a colorimetric method due to presence of organic P in the extracts.
Chamber Systems for Measuring Nitrous Oxide Emission from Soils in the Field
Authors: Denmead O. T.
Published: July 2010

Recent concern over N2O losses from soils has highlighted the need for new techniques for measuring N2O exchange in the field. Two systems are described, in which nondispersive infrared gas analysis is used to measure the change in N2O concentration of air passing through a cylindrical chamber driven 0.1 m into the ground. When interfering gases are removed from the air stream, the infrared analyzer has a resolution of ± 12 ppb N2O.

In one system, air circulates in a closed loop between the chamber air space and the gas analyzer; in the other, open system, outside air is drawn continuously through the chamber space and its N2O enrichment or depletion measured.

Two operational problems (common to many emission chambers) were encountered: the development of a low pressure in the chamber when air is withdrawn, which induces a mass flow of N2O from the soil in addition to the diffusive flow; and a readjustment of the N2O concentration in the soil air whenever the N2O concentration in the chamber air changes from ambient. These can lead to incorrect estimates of the flux. The former problem was overcome by chamber design. The latter appeared to be insurmountable in the closed system, but could be reduced to acceptable proportions in the open system by choice of air flow rate.

The open system permits relatively rapid equilibration, automatic and continuous operation, a discrimination less than 2 ng N m−2 sec−1, and the maintenance of environmental conditions within the chamber close to those in the field.
The Release of Sulfate from Soil‐Applied Basaluminite and Alunite
Authors: Wolt J. D. , Adams Fred
Published: July 2010

Release of SO4 from synthetic basaluminite and alunite was measured by plant uptake after mixing various rates of these compounds with Marvyn loamy sand at pH 6.5. The fraction of SO4 released from basaluminite was about one‐half that from gypsum, according to S uptake by cotton plants. Alunite released very little SO4. Release of SO4 by basaluminite in soil supports the thesis that SO4 retention and desorption in acid soils can be explained in part by solubility of Al‐hydroxysulfates.
Salinity Profiles and Leaching Fractions for Slowly Permeable Irrigated Field Soils
Authors: Lonkerd W. E. , Ehlig C. F. , Donovan T. J.
Published: July 2010

The salinity status of four slowly permeable irrigated soils was measured under commercial field conditions to determine the magnitude and variability of actual leaching fractions. Soil cores were taken in 30‐cm increments to a 150‐cm depth. Assuming a desirable leaching fraction of 15 to 20% for lettuce (Lactuca sativa L.), and 5 to 10% for alfalfa (Medicago sativa L.), cotton (Gossypium hirsutum L.), sugarbeet (Beta vulgaris L.), and wheat (Triticum aestivum L. em Thell.), for nearly all soil‐crop combinations, leaching fractions ranged from insufficient to excessive. Median leaching fractions were excessive in Holtville and Indio soils planted to lettuce, sugarbeet, and wheat and insufficient or marginal in Imperial and Meloland soils planted to all crops.
Ammonia Volatilization from Surface Applications of Urea in the Field and Laboratory
Authors: Hargrove W. L. , Kissel D. E.
Published: July 2010

Few attempts have been made to directly measure ammonia losses from surface applications of urea under field conditions. The objective of this research was to measure NH3 volatilized from urea in the field and to compare these losses to (i) losses measured in the laboratory, and (ii) losses estimated by crop response in the field. Direct field measurements were made using an automated apparatus designed to collect NH3 lost without significantly altering environmental conditions on the treated area. Laboratory measurements were made using an apparatus similar to systems described previously by other workers. Ammonia losses were estimated from crop response in the field by measuring N uptake by Coastal bermudagrass (Cynodon dactylon L.).

Losses of NH3 in the field measured directly were small (0 to 9% of the applied N) compared to those obtained in the laboratory (13 to 31% of the applied N) and those estimated in the first year of the N uptake study (0 to 39% of the applied N). However, in the second year of the field plot study, N uptake by forage from several urea fertilizer treatments was greater than from Ca(NO3)2. When the results were combined for both years, N uptake by forage was similar from Ca(NO3)2 and urea treatments. Considering the small ammonia losses measured directly in the field, differences in crop response between urea and Ca(NO3)2 may have been due to some factor other than NH3 volatilization.

Results indicate that losses of N by NH3 volatilization under field conditions may not be as severe as previously thought, at least under the soil and environmental conditions of this study. Results also demonstrate the importance of directly measuring NH3 losses in the field.
Irrigation System Effects on Applied Fertilizer Nitrogen Movement in Soil
Authors: Onken Arthur B. , Wendt C. W. , Wilke O. C. , Hargrove R. S. , Bausch Walter , Barnes Larry
Published: July 2010

Movement of unused fertilizer nitrate‐nitrogen (NO3‐‐N into shallow underground water strata by way of irrigation return flows has become a concern as irrigation has increased. Previous research has been largely conducted with furrow and sprinkler irrigation systems in areas of low rainfall and in many cases in the absence of a growing crop. We studied, directly in the field, the effects of furrow, sprinkler, and subirrigation on the movement of fertilizer NO3‐‐N in a supplementally irrigated area in the presence of sweet corn (Zea mays L.).

Sodium nitrate enriched with 15N was band applied below the surface at rates of 124 and 105 kg of N/ha in 1973 and 1974, respectively. Soil samples were periodically taken in 30‐cm vertical increments through each fertilizer band, the center of the bed and beneath each furrow. Under sprinkler irrigation the fertilizer bands tended to move down with somewhat less lateral movement close to the soil surface than with the other systems. Also, movement out of the surface 30 cm was faster than for the other irrigation systems. Under furrow irrigation the fertilizer tended to move toward the center of the bed and then moved downward. With subirrigation the fertilizer moved upward and outward toward the furrows and then moved downward. The fertilizer remained in the upper 30 cm of soil longest with subirrigation.
Salt Effects on the Hydraulic Conductivity of a Sandy Soil
Authors: Pupisky H. , Shainberg I.
Published: July 2010

The changes in the hydraulic conductivity of a Red Brown sandy soil as a function of the concentration and SAR of the percolating solutions were measured. Also, the changes in the hydraulic heads along the soil column and analysis of the salt and clay concentrations in the effluent solutions were recorded. The data show that at high ESP's and at salt concentration above 0.01N, swelling of the clay is the main mechanism responsible for hydraulic conductivity decrease. At low ESP and very dilute soil solutions, dispersion and clay migration into the conducting pores are the main mechanisms responsible for plugging the soil pores. Dispersion of the clay particles is possible only when the concentration of the soil solution drops below a threshold concentration at which the clay platelets flocculate. Dispersion of the clay may lead also to an increase in hydraulic conductivity when a sandy soil is leached with distilled water.