bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption of Phosphate by Hydroxy‐Aluminum Species on a Cation Exchange Resin
Authors: Robarge W. P. , Corey R. B.
Published: July 2010

A study was conducted to provide a possible explanation for the reported decrease in the concentration of P in soil solutions with increasing pH and/or ionic strength. The assumption was made that P in solution decreases because of the formation of a new P‐adsorbing surface, the source of which would be exchangeable Al3+. An Al‐saturated resin was used as a model of an acid soil to study the effects of pH, charge and/or concentration of associated cation on the concentration of P in solution when the P‐adsorbing complex is affixed to a negatively charged surface. The hydroxy‐Al species formed by adding base was found to be the primary P‐adsorbing surface. The OH/Al molar ratio of the hydroxy‐Al species formed remained nearly constant with addition of base (2.0 to 2.1:1 in the presence of Ca(ClO4)2; 2.4:1 in the presence of NaClO4; µ = 0.003) until all the Al3+ present had been converted to the hydroxy‐Al form. The pH of formation of the hydroxy‐Al species was a function of µ and neutral salt cation.

Phosphate was added at Al/P molar ratios of 12:1 or 6:1 in the presence of Ca(ClO4)2 or NaClO4 of equal ionic strengths (µ = 0.0003 or 0.003). The hydroxy‐Al species demonstrated a marked capacity to adsorb P. At an Al/P molar ratio of 2.0:1 (Ca(ClO4)2; µ = 0.003) the equilibrium concentration of P was < 0.2 mg/l. As % neutralization of exchangeable Al3+ increased, at constant total P concentrations, P in solution initially decreased, passed through a minimum, and then increased. The pH of minimum P in solution corresponds to the point where increased adsorption due to increasing adsorbing surface is balanced by increasing competition from hydroxyl ions for adsorption sites. Exchangeable Al3+ did not react with added P until the Al/P ratio of the hydroxy‐Al species equalled or became less than 2.0:1.

The effects of µ and pH on P adsorption in the Al‐resin system are similar to many results reported in the literature for soil systems. Our studies suggest that the often observed correlation between exchangeable Al3+ and P fixation by soils is due to the relationship between Al3+ and the formation of the hydroxy‐Al species, unless the P addition rate is high enough to favor the precipitation of an aluminum‐phosphate compound. Hydroxy‐Al species formed by liming acid soils to above the pH at which all exchangeable Al3+ is converted to nonexchangeable forms appear to be stable enough to affect the concentration of P in solution over the short‐term, but may be unstable with respect to gibbsite or other Al minerals over long periods of time.
Nodulation of Trifolium subterraneum L. by Introduced Rhizobia in Southwest Oregon Soils
Authors: Hagedorn Charles
Published: July 2010

The establishment of Trifolium subterraneum L. in response to inoculation and fertilization treatments was determined at five field sites in southwest Oregon. Both strains of Rhizobium trifolii (TA1 and C6) were capable of successful nolulation of subclover (c. v. Mt. Barker) at all sites although differences in performance of the strains occurred at three locations. Fertilization (P, S, and Mo) significantly increased the overall nodulation of the plants as well as the proportion of nodules occupied by the inoculum strains. Both plant dry weights and total N levels reflected an additive effect of inoculation and fertilization. Results indicated that subclover appeared to be a suitable crop for hill pastures in western Oregon and, with adequate fertilization and a suitable inoculum, the subclover and the amended rhizobia can become established and productive during the first growing season.
Mottling and Iron Distribution in a Glossoboralf‐Haplaquoll Hydrosequence on a Glacial Moraine in Northwestern Wisconsin
Authors: Richardson J. L. , Hole F. D.
Published: July 2010

Distribution of iron oxide and forms of mottling and cutans under various moisture regimes were studied in a Woodfordian glacial moraine landscape. Hydrosequence members were observed and sampled along two transects in adjacent first‐order drainage basins. Considerable iron had been translocated out of the A horizon and either into the B horizon or out of the solum, in all pedons studied. Mottle development followed an expected systematic sequence from none at well‐drained (WD) sites, where unsaturated movement of water predominates; to considerable at somewhat poorly drained (SPD) sites, where saturated flow occurs frequently and where the dry‐wet cycle is characteristic; to few at very poorly drained (VPD) sites where gleying has been favored by stagnant water conditions in wet seasons. At WD sites mottles were either absent or of low chroma both in the interiors and on the faces of peds. At SPD sites mottles were of low chroma on ped faces and of high chroma inside peds, and Fe‐Me concretions were relatively abundant. At VPD sites neutral gray hues predominated both inside peds and on surfaces of macrospores, and there were only a few iron concretions or, at wettest sites, “pipestems.” Changes in distribution of iron extractable by aqua regia, dithionite and oxalate characterized the degree of crystallinity of iron compounds in the sequence. Iron oxides were most crystalline at WD sites where they tended to concentrate in the clay fraction. Iron oxides were concentrated in sand‐size concretions at SPD sites.
Carolina Bays on the Eastern Shore of Virginia
Authors: Bliley D. J. , Pettry D. E.
Published: July 2010

Carolina bays were analyzed on the Eastern Shore of Virginia utilizing infrared imagery and pedologic techniques. Over 160 bays were delineated thus indicating they are major landforms in the area. Bays differed from those reported in other regions by being less elliptical, more westerly oriented, and lacking well‐developed rims in any specific quadrant. Bay location and size are apparently controlled by landscape and sandy parent materials as evidenced by association with less distinct natural depressions with similar orientation as the related geomorphic urface. Soils on bays of recent surfaces have weaker profile development compared to Pleistocene upland bays. More than one period of bay formation is suggested by differential pedogenic development and geomorphic positions. Data indicate Carolina bays were formed by the alteration of poorly drained areas on undissected Coastal Plain interfluves. Wind and waves are suggested as factors in bay formation based on well‐sorted sands of elevated rims, “dune‐like” character, and silt content of possible aeolian origin.
Urea‐Ammonium Sulfate and Urea‐Ammonium Phosphate Evaluation as Nitrogen Sources in the Southeast
Authors: Walker M. E. , Keisling T. C. , Marchant W. H. , Morey D. D.
Published: July 2010

Recent increases in N fertilizer cost emphasize the need for information concerning the use of cheaper N sources to produce the most marketable yield per unit fertilizer cost. Urea‐ammonium sulfate (UAS) and urea‐ammonium phosphate (UAP) are two new fertilizer products in which urea is the main source of N. These materials were compared to ammonium nitrate (AN) as N sources for corn (Zea mays L., Coastal bermudagrass (Cynodon dactylin L. Pers.), and rye (Secale cereale L.).

Each material was used to supply N at rates from 0 up to 448, 336, and 135 kg/ha on Coastal bermudagrass, corn, and rye, respectively. All crops were grown on Tifton soil (Plinthitic Paleudult; fine, loamy, siliceous, thermic). Corn was also grown on a Greenville soil (Rhodic Paleudult; clayey, kaolinitic, thermic). Recommended cultural practices normally used in the area were followed for each crop. Forage yield for Coastal bermudagrass and rye was measured and selected samples analyzed for ammoniacal N concentration. Corn grain yield was measured. Selected soil samples from the corn experiment were analyzed for nitrate‐N.

Percent N increased in Coastal bermudagrass and rye forage as N application rate increased. Coastal bermudagrass recovered less N from both UAP and UAS than from AN at the 336 kg/ha N rate. All materials were equivalent as N sources for rye and corn. Irrigation of the corn was found to increase yields as well as nitrate‐N leaching. Applying 50% of the 336 kg/ha N at planting and the rest later to prevent leaching in corn production was no better on Tifton and Greenville soils than a single preplant N application of either 168 or 336 kg/ha. For Southeastern Coastal Plain conditions the two fertilizers evaluated could replace AN in corn and rye production without loss in N concentration, yield, or N use efficiency. The materials tended to be less efficient than AN in supplying N for Coastal bermudagrass production.
Mineralogy of Soils Developed on Pliocene‐Pleistocene Terraces of the Tombigbee River in Mississippi
Authors: Nash V. E.
Published: July 2010

The clay minerology of four soil pedons formed on Pliocene‐Pleistocene terraces was investigated. These pedons are in the Typic Hapludult, Typic Fragiudult, Aquic Fragiudult, Typic Ochraqualf subgroups and vary, respectively, in drainage from well drained to poorly drained. Smectite was the major mineral in all of the clay fractions with the maximum quantity usually coinciding with the zone of maximum clay accumulation. Hydroxy Al‐interlayered 2:1 clay was generally confined to the upper horizons of these soils. In the deeper horizons, particularly for the poorly drained Aquic Fragiudult and Typic Ochraqualf, the polymeric Al interlayers were replaced by Al(H2O)63+. These soils are all very acid and in the deeper horizons, which are continuously wet, Al‐polymers do not form. In cases where hydroxy Al‐interlayered minerals were deposited by sedimentation the Al‐polymers have been removed. Evidence is presented for a low charge smectite (montmorillonite) and a high charge smectite (beidellite) in these soils. In the surface horizons beidellite is the dominant species with Al‐interlayers, however in the deeper zones both types of smectite are found.
Differential Thermal Characteristics of Soil and Reference Quartz
Authors: Barwood H. L. , Hajek B. F.
Published: July 2010

Forty‐two reference quartz and soil quartz samples were analyzed by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). A single α‐β endothermic peak was obtained from 35 samples. Seven samples gave multiple endothermic peak curves. Although XRD indicated that most samples were essentially 100% α‐quartz, DSC peak height to width at one‐half peak height ratios of single peak curves ranged from 5.85 (quartz from sedimentary rocks) to 24.06 (igneous and metamorphic rock quartz). DSC height‐width peak ratios can be used to identify the origin of soil quartz to a specific geologic province (igneous, metamorphic, sedimentary). An apparent variation in quartz ΔH makes quantitation of soil quartz by thermal methods difficult. All but one of the multi‐peaked curves were obtained from vein quartz. No soil quartz showed multiple peaks.
Physical Components of the Diffusivity Coefficient
Authors: Malik R. S. , Laroussi Ch. , De Backer L. W.
Published: July 2010

Isothermal horizontal infiltration experiments were conducted in 53–63 µm, 74–88 µm, or 105–125 µm glass bead fractions with water, 6% ethyl alcohol water solution, 20% ethyl alcohol water solution, ethyl alcohol, and methyl alcohol. From these experiments, the diffusivity coefficient was determined using the Bruce and Klute (1956) procedure and D(θ) was established for the fluid content, θ, from 0% to saturation.

The D(θ) variation in the fluid content range between 3 and 30% was investigated. The functional relationships between D(θ) and the properties of the fluid, the geometry and the solid matrix were investigated. The physical components of D(θ) were determined using:
urn:x-wiley:03615995:saj2sssaj197903615995004300040001x:equation:saj2sssaj197903615995004300040001x-math-0001 where r* and R* are the mean radius of pores and beads, respectively, σ, µ and ΔHv are the surface tension, viscosity and molar heat of vaporization of the fluid, respectively, and α is the fluid‐solid contact angle.

The physical significance of the diffusivity coefficient given by Laroussi and De Backer (1975) defining this coefficient as the ease with which the fluid particles spread from a wetting front, is clarified and confirmed.
A Galerkin in Time, Linearized Finite Element Model of 2‐Dimensional Unsaturated Porous Media Drainage
Authors: Cushman John H. , Kirkham Don , Keller Roy F.
Published: July 2010

Two‐dimensional drainage in porous media by a modified finite element technique is examined. This technique consists of using Galerkin's method on the temporal as well as the spatial dimensions and coupling it with a simple linearizing scheme (considering physical properties constant over individual elements).

We apply this method to four separate drainage problems, two of which have been studied previously by other authors. With both of the previous studied problems, our results compared well.
Nature and Properties of Water in Montmorillonite‐Water Systems
Authors: Low Philip F.
Published: July 2010

Data are presented on several properties of water in montmorillonite‐water systems. The data indicate that these properties differ from the same properties of bulk water because of differences in intermolecular bonding. Also, it is found that the value, J, of each property is described by the general equation J = J° exp β/(mw/mm) in which J° is the value of the given property in pure bulk water, mw/mm is the mass ratio of water to montmorillonite and β is a constant. The proposal is made that, since all of the water properties obey a common equation, their deviation from the corresponding properties of bulk water must be caused by a common factor. By making appropriate substitutions for mw/mm and analyzing the resulting equations, the common factor is shown to be interaction of the water with the surfaces of the montmorillonite layers. The nature of this interaction, and ways in which it might affect intermolecular bonding, are discussed.
Use of Gypsum Stones to Lower the Sodium Adsorption Ratio of Irrigation Water
Authors: Ahmad Bashir , Kemper W. D. , Haider Ghulam , Niazi M. A.
Published: July 2010

Many sources of irrigation water have sufficiently high Na+/Ca2+ ratios to be harmful to soils and crops. When the salt contents of the waters are reasonably low, the primary method of lowering this ratio is to apply extra Ca2+ on the fields or in the water. Gypsum is generally the most reasonably priced source of Ca2+. A major portion of its current cost is associated with grinding the stones to a powder and application of this powder to the fields.

This study shows that gypsum stones 5 to 20 kg in size are a useable source of the Ca2+ needed to bring down the sodium adsorption ratio (SAR) in sodic irrigation waters. The dissolution rate of the gypsum stones is proportional to the square root of the velocity of flow through the bed. Since the time of residence of solution in the bed is inversely proportional to its velocity through the bed, the increase in concentration of Ca2+ in solution as it passes through the whole bed is inversely proportional to the square root of the velocity of flow. Solution concentration is also inversely proportional to the square root of the size of the stones in the bed.

Equations were developed to facilitate design of channels with the proper cross section and length to supply the needed amounts of Ca2+ to the water when the average size of the stones, the flow rate of the water, and the initial ionic concentration of the water are known.
Comparison of Methods to Extract Spores of Vesicular‐Arbuscular Mycorrhizal Fungi
Authors: Smith Garriet W. , Skipper Horace D.
Published: July 2010

Vesicular‐arbuscular mycorrhizal spores were extracted from soil (pot cultures) using adhesion‐flotation, sucrose‐centrifugation, gelatin column, wet‐sieve, and a new plating method. Counts of 150‐ to 300‐µm diam spores were significantly higher for the plate method by 528, 370, and 258% than for the adhesion‐flotation, sucrose‐centrifugation, and gelatin column methods, respectively. Counts of 100‐ to 300‐µm diam spores were higher for the plate method by 200 and 149% than for the wet‐sieve and modified wet‐sieve methods. Spore counts within four spore size ranges (50 to 100, 100 to 150, 150 to 300, and > 300 µm diam) were greater for the plate method than for the wet‐sieve and modified wet‐sieve methods by approximately four and two times, respectively. The plate method was consistently higher than the wet‐sieve method only for small spores (50 to 100 µm diam) from soybean field soils. Although the new plate method is not applicable for extracting and quantifying large spores (> 100 µm diam) for low spore population soils (field soils), it is recommended for the purpose of quantifying spores in high population soils (> 20 spores/g) as might be encountered in pot cultures.
Studies of Nitrous Oxide Emission from a Grass Sward
Authors: Denmead O. T. , Freney J. R. , Simpson J. R.
Published: July 2010

The exchange of nitrous oxide (N2O) between soils and the atmosphere is believed to play an important part in controlling stratospheric ozone levels, but so far, very little information is available on rates of emission or absorption of N2O by soils in the field. The paper reports measurements of N2O exchange made over 5 months from winter to summer in an unfertilized, mown, grass sward.

Ambient air was drawn continuously in an open flow system through the above‐ground portion of a steel cylinder driven into the ground. The enrichment or depletion of N2O in the air stream was measured with an infrared gas analyzer. Exchange rates as small as 1 ng N m−2 sec−1 could be measured.

Nitrous oxide was always emitted from the sward, even at very low soil moisture contents. The emission showed a clear diurnal cycle in phase with the temperature of the surface soil; peak emission rates occurred in the afternoon, minima near sunrise. Additions of water as small as 5 mm increased emission rates markedly. Both results suggest that most of the N2O was produced close to the soil surface rather than at depth in the soil profile. Further, the production of N2O was accompanied by a net increase in soil nitrate.

Emissions were largest in the spring. With the soil moist to less than field capacity, average daily emissions over periods of several days ranged from 0.6 to 2.5 mg N m−2.
Aluminum Accumulation and Tolerance of Triticale and Wheat in Relation to Root Cation Exchange Capacity
Authors: Mugwira L. M. , Elgawhary S. M.
Published: July 2010

Since plant characteristics associated with Al tolerance vary from one species to another, the objective this study was to relate Al tolerance, Al accumulation, root Cation Exchange Capacity (CEC), and exchangeable Al in triticale (X Triticosecale, Witt Mack) and wheat (Triticum aestivum L.). Ten cultivars of the two species were grown in nutrient solutions with 0 or 6 ppm Al added. The solutions were adjusted to pH 4.8 either at transplanting or daily during plant growth. Aluminum accumulation and displacement by Ca and K from roots exposed to Al for up to 24 hours were also determined. With the solution pH adjusted only at transplanting, the relative root lengths (Al/no Al) indicated that the order of Al tolerance was 6TA 298 and 6TA 131 > 6TA 385 > 6TA 203 triticale and Atlas 66 > Thorne and Seneca > Monon > Redcoat and Arthur wheats. Similar Al tolerance ratings were obtained when solutions were adjusted daily to pH 4.8. Correlation coefficients between relative root lengths and root Al concentrations were −0.93** and −0.90** for triticale and −0.85** and −0.063 for wheat, respectively with pH unadjusted and pH adjusted. Correlation coefficients between plant‐induced pH values and root Al concentrations were −0.19 for triticale and −0.79** for wheat. The root CEC values were generally lower in Al‐tolerant than Al‐sensitive cultivars. The results also suggested that the CEC of roots may be a factor in controlling Al absorption in the first 6 hr of plant exposure before the exchange sites are Al‐saturated at longer periods.
Influence of Surface Roughness and Clod Size and Stability on Soil and Water Losses
Authors: Johnson C. B. , Mannering J. V. , Moldenhauer W. C.
Published: July 2010

Rough cloddy surfaces increased infiltration and decreased soil erosion compared to smoother surfaces as determined by simulated rainfall studies. Overtilling reduced surface roughness and cloddiness. One field experiment showed that a rough surface decreased runoff by 77% and soil erosion by 89% of that from a smooth surface. Tillage of wet soil increased surface roughness, but another field experiment showed that clods resulting from plowing the soil when wet were quite unstable compared with clods from plowing nearer the upper plastic limit. Tilling of compacted soil results in greater cloddiness than tilling of uncompacted soils. However, a laboratory experiment showed that compacted loam clods were less resistant to breakdown by water drop energy than those from uncompacted soil. Compaction of silty clay loam and silty clay soils did not change their stability significantly. To be effective as an erosion control measure, soil clods must be large enough and stable enough to keep infiltration at a high level until the crop canopy covers the soil surface. These studies describe the size and stability necessary to maintain a high level of runoff and erosion control.
Cation Exchange and Selectivity in Heated Minerals
Authors: Komarneni Sridhar
Published: July 2010

Various minerals that are commonly present in shales were heated in air as well as hydrothermally and their cation exchange capacity (CEC) and cation exchange selectivity (CES) values were determined. The CEC values of all the heated minerals decreased because of partial or complete collapse of the layers.

The CES (KX/Ca1/2X) values of montmorillonites and micaceous vermiculites increased because of wedge site formation by partial collapse after heat treatment to 500 and 750°C in air. The CES values of coarse grained micas, however, decreased by dry heat treatment because of the collapse of frayed edges or wedge zones. Heated illites randomly interstratified with montmorillonite behaved like the specimen montmorillonites, while heated, well crystallized illites behaved similarly to the coarse grained micas. That the wedge zones are enormously selective for potassium was clearly proven here by the collapsed, heated minerals.

The CES values of poorly crystalline illites interstratified with montmorillonite increased while those of well crystallized illites with discrete vermiculite impurity decreased upon hydrothermal treatment at 400°C and 500 bar (pressure). The decrease or increase in CES of the hydrothermally heated illite minerals can be explained by the loss or creation respectively of wedge zones just as in the case of air‐heated minerals.
Measurement of Apparent Electrical Conductivity of Soils by an Electromagnetic Induction Probe to Aid Salinity Surveys
Authors: de Jong E. , Ballantyne A. K. , Cameron D. R. , Read D. W. L.
Published: July 2010

A noncontacting soil resistivity probe, based on electromagnetic induction, was used to measure soil salinity. Good correlations were obtained between the apparent bulk soil conductivity measured by the instrument and the electrical conductivity of saturated paste extracts or the bulk electrical conductivity measured by the Wenner four‐probe method. The electromagnetic induction technique provided less detailed information on salinity changes with depth than the other methods, but was faster and can provide a continuous record of salinity changes along a transect.
Ion Chromatographic Determination of Sulfate and Nitrate in Soils
Authors: Dick W. A. , Tabatabai M. A.
Published: July 2010

A simple and precise ion chromatographic (IC) method for determination of SO42‐ and NO3‐ in soils is described. It involves determination of these anions in soil extracts by using a Dionex Model 10 Ion Chromatograph. An aliquot (≃2 ml) of soil extract is injected in the eluent stream (3.0mM NaHCO3 + 1.8mM Na2CO3), and the anions are separated by an analytical column containing Dionex low‐capacity anion‐exchange resin in the HCO3‐ form and converted to the corresponding acids by a suppressor column containing a strong acid cation‐exchange resin in the H+ form. Conductivity is used as the mode of detection. Results of SO42‐ and NO3‐ in soils by the IC method agreed closely with those obtained by the methylene blue and steam‐distillation methods, respectively. Tests indicated that S2‐, SO32‐, S2O32‐, S2O52‐, S4O62‐, SCN‐, thiourea, glucose‐6‐sulfate, and p‐nitrophenyl sulfate do not interfere in determination of SO42‐. Also, NO2‐ does not interfere in determination of NO3‐. This method gives quantitative recovery of SO4‐S and NO3‐N added to soils (5–50 µg/g soil). The detection limit is 1 µg SO4‐S or NO3‐N/g soil (0.2 µg SO4‐S or NO3‐N/ml of soil extract). With the IC method, SO4‐S and NO3‐N can be determined simultaneously in about 10 min.
Mineralization of Carbon and Phosphorus from Carbon‐14 and Phosphorus‐32 Labelled Plant Material Added to Soil
Authors: Dalal R. C.
Published: July 2010

Soil receives a large amount of P annually through above and below ground plant materials and animal excretions. This P in these materials becomes available to the growing plants through microbial decomposition. Since P mineralization follows C mineralization (CO2 loss), both C loss and P mineralization (measured by the amount of P utilized by oats (Avena sativa L.) from the added roots and tops of 14C‐ and 82P‐labelled white clover (Trifolium repens L.) were assessed for 10 weeks in the controlled environment chambers (26°C/16°C, 12‐hour day/night temperature). By 10 weeks, 42 and 38% of applied P was utilized by oats from the roots and tops, respectively. During the same period, about 55 and 70% of the C was lost from the roots and tops, respectively, of the added plant material. The half‐lives, t1/2, of 82P utilization from the roots and tops were 10.8 and 12.4 weeks, respectively. The corresponding t1/2 of 14C mineralization were 15.3 and 8.1 weeks in the presence of plants and 15.2 and 9.7 weeks in the absence of plants.

After the initial rapid loss of C, P mineralization followed C mineralization (or loss) of the added plant material closely. Since the decaying of roots and tops of crop plants and pastures in the field release P upon mineralization, this factor should be considered in soil P management practices.
The Effect of Roots on Soil Denitrification
Authors: Smith M. Scott , Tiedje James M.
Published: July 2010

The effects of plant roots on denitrification were studied using the acetylene inhibition method, both with short‐term anaerobic assays for potential denitrifying activity and with intact plants in soil. Experiments with anaerobic assays demonstrated that denitrification activity was greater in the rhizosphere of both pot and field grown plants. A split‐plate technique showed that potential denitrifying activity decreased rapidly in the first few millimeters away from roots. These effects were shown to be due, at least in part, to differences in available organic matter.

A new method was developed for measuring short‐term denitrification rates of soils with intact plants in an aerobic atmosphere. The soil conditions in these assays were comparable to field conditions. When soil NO3‐ concentrations were high, the results confirmed prevailing opinion that denitrification rates are increased in the rhizosphere. In contrast, the planted soils denitrified at significantly lower rates than unplanted soils when NO3‐ concentrations were low. Thus, denitrification may sometimes be reduced in the rhizosphere. These experiments also indicated that increasing NO3‐ concentration increased the ratio N2O/(N2 + N2O), but that the roots had no consistent effect on this ratio.
Survival of Rhizobium in Soils Undergoing Drying
Authors: Pena‐Cabriales J. J. , Alexander M.
Published: July 2010

Streptomycin‐resistant mutants of Rhizobium were used to study Rhizobium survival in soils undergoing drying. The decline in numbers of R. japonicum in soil was biphasic. The initial, rapid phase coincided with the time of major water loss, and the subsequent slow rate of decline of viability occurred as the soil lost little water. Similar population charges were found with other species of Rhizobium. The rate of dying of R. japonicum and R. leguminosarum during the second phase in soil at relatively low moisture levels was governed by the water content of the soil. In 10 days of drying, the cell numbers of the six Rhizobium species and a cowpea Rhizobium were reduced by two logarithmic orders of magnitude, and no differences in susceptibility were noted between the fast‐ and slow‐growing rhizobia. Exposure of R. japonicum to several cycles of wetting and drying resulted in a further reduction in population size with each cycle. The percentage survivors of R. japonicum was not greatly affected by the time required for the drying but was different in different soils. Rhizobia that proliferated in soil showed somewhat better survival than those grown in culture and added to soil. Decayed organic residues afforded little protection against desiccation, but placing the root‐nodule bacteria in a suspension of the polysaccharide they elaborate allowed for somewhat better survival.
Chemical and Mineralogical Properties of the Fragipans of the Cincinnati Catena
Authors: Steinhardt G. C. , Franzmeier D. P.
Published: July 2010

This is a study of fragipan soils on two transects on the Illinoian till plain of southern Indiana. These soils were thought to be formed in 50 – 100 cm of loess over Illinoian Age till. In the soils sampled for this study, the surface of Sangamon Age paleosol in Illinoian till was located at a 2‐m depth. Two other parent materials above the paleosol were described. The surface parent material may be loess, but the parent material above the paleosol is too sandy to be completely loess.

In sodium citrate‐bicarbonate‐dithionite extracts, SiO2 contents reached a maximum in the fragipan horizons. The Al2O3 contents were highest in the argillic horizon. Extraction of natural clods from the fragipan matrix by various solutions under vacuum showed that extractants that removed Fe and Al did not affect the cohesion of the fragipan matrix. Silica was extracted by sodium hydroxide which also broke down the fragipan matrix. Carbonate and bicarbonate solutions also broke down the fragipan matrix and may have caused a reaction between soluble Si and the soil material. Thus we consider Si to be the binding agent, along with clay, that produces the characteristic brittleness of the fragipan horizon.
Factors Affecting Release and Plant Availability of Sulfur‐Coated Micronutrients
Authors: Ryan John , Prasad J. Devi
Published: July 2010

The agronomic effectiveness of S‐coated micronutrients and factors influencing their dissolution were studied in the green‐house and laboratory. Grain sorghum (Sorghum vulgare L.) was grown for 7 weeks on a calcareous soil incubated individually with S‐coated and uncoated FeSO4·7H2O, MnSO4·H2O, and ZnSO4·7H2O for 0, 1, 2, 3, 5, and 8 weeks. Dry matter yield was not significantly affected, but Fe and Mn uptake decreased with time of incubation prior to cropping. Values from S‐coated materials were initially higher than from uncoated materials but showed little differences after 8 weeks of incubation.

Coated materials were incubated for up to 9 weeks at varying moisture contents (8–32%), temperature (8–35°C), Ca(OH)2(1–10%) and sucrose (0.5–2 g). DTPA‐extractable Fe, Mn, and Zn in treated soils decreased with incubation time and with increasing moisture, temperature and Ca(OH2) levels while the effect of sucrose additions was variable. With continuous extraction of the granules in water and in soil by DTPA at 4‐day intervals for 71 days, most of Fe, Mn, and Zn was released during the 1st month. Oxidation of the S‐coatings enhanced native micronutrient availability. Unless improvement in coating materials is made, S‐coated micronutrients are unlikely to have a significant impact in micronutrient fertilization.
Atrazine Degradation and Residue Distribution in Soil
Authors: Dao T. H. , Lavy T. L. , Sorensen R. C.
Published: July 2010

Degradation and its effect on atrazine leaching were observed in soil in the laboratory. Degradation of 1.5 ppmw (wt/wt) of ring labeled 14C‐atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) over time periods up to 8 months was predominantly a nonbiological process in three nonsterilized soils at 0.1 bar moisture content, although there was evidence that the atrazine molecule was dealkylated simultaneously. Between 4 and 17% of the applied 14C was present as nonpolar compounds after 1 month of incubation at 30°C. The amount of 14CO2 evolved was cumulatively less than 0.05% of the added radiocarbon at 5 and 30°C. Desorption of atrazine from soil treated and incubated for 0.5 hour; 1 and 2 weeks; 1, 2, 4, and 8 months showed a steady increase in the unextractable fraction remaining in soil with time. In the soil extract, a tolueneinsoluble fraction increased as time passed, and made up between 24 and 62% of the extracted radiolabeled fraction of the three soils after 1 month of incubation at 30°C. The ratio of polar compounds to nonpolar compounds steadily increased with time of incubation. Major possible metabolites of the toluene‐soluble fraction were identified by thin layer chromatography as monodealkylated products. During elution of atrazine from soil columns saturated with water, decreasing the water flow rate from 2 cm/hour to 0.08 and 0.04 cm/hour greatly reduced the downward movement and enhanced degradation of the herbicide.
Fluorine in Agricultural Soils of Southeastern Pennsylvania
Authors: Gilpin Lawrence , Johnson Arthur H.
Published: July 2010

Three fractions of fluorine were measured in a variety of Pennsylvania soils using a fluoride electrode. Mean total, soluble and resin‐extractable F values for 55 samples were 377±27, 0.38±0.5 and 21.7±1.6 ppm, respectively, in a variety of soils typical of the Piedmont and Triassic Lowlands of southeastern Pennsylvania. Each of the F fractions was related to soil pH. Selected soils were leached with a standard F solution and found to retain substantial amounts of F.
Application of Elovich Equation to the Kinetics of Phosphate Release and Sorption in Soils
Authors: Chien S. H. , Clayton W. R.
Published: July 2010

Experimental data on the phosphate release and sorption in soils, when inadequately described by a first‐order kinetic reaction, are often interpreted as a combination of two or three simultaneous first‐order reactions. A simple modified Elovich equation in the form: q = (1/β) ln (αβ) + (1/β) ln t was derived to fit the reported experimental data in literature that failed to conform to a single first‐order kinetic equation. In this equation, q is the amount of phosphate released or sorbed, and α and β are constants. The equation successfully described the data as a single straight line that covers the entire course of reaction time. It also appears that constants of α and β may be used for comparison of reaction rates of phosphate release or sorption in different soils.
Phosphate Fractions in Calcareous Soils as Altered by Time and Amounts of Added Phosphate
Authors: Hooker M. L. , Peterson G. A. , Sander D. H. , Daigger L. A.
Published: July 2010

Tie‐up of water‐soluble P is very rapid in calcareous soils. To determine the residual effect of high rates of applied P several experiments were established on soils ranging from 0.1 to 16.5% calcium carbonate equivalents (CCE). At each location an experiment was established with four rates of P (25, 50, 100, and 500 kg/ha). The soils were sampled annually for periods of up to 5 years. These soil samples were fractionated to determine the concentration of P in the various inorganic P fractions, using the techniques of Syers et al. (1972), as affected by rate of P application and time after application.

Over time there was a decrease in the more soluble, plant‐available fractions indicating a shift of P from extractable to nonextractable forms. Also the various P fractions were correlated with two of the more commonly used soil methods, Bray and Kurtz no. 1 and the Olsen NaHCO3. As the CCE of the soils increased the correlation of the Bray and Kurtz no. 1 method with the fractions considered most available to plants decreased while the correlation of the Olsen method remained high.
Physical Characteristics of Some Minesoils
Authors: Pedersen T. A. , Rogowski A. S. , Pennock R.
Published: July 2010

Studies were conducted to evaluate physical properties of spoils resulting from surface‐coal mining and reclamation operations in Clearfield County, Pennsylvania. Bulk density, evapotranspiration, water retention, infiltration, and hydraulic conductivity values were determined at 10 sites randomly located within a 4‐ha experimental area. Average bulk density of the surface 0.5‐m layer of minesoil was 1,763 kg/m3 while specific surface at most sites averaged 31 m2/g. Microlysimeter data indicated that evapotranspiration (ET) on minesoil could be approximated by class‐A pan evaporation or by model results. A large amount of spatial variation was observed in infiltration, water retention and hydraulic conductivity values. In the uppermost 0.75 m of the profile most minesoils on the average retained 35 mm of water, between 10 and 1,500 kPa, compared to 136 mm for the adjoining soils. When water was avaliable ET approached potential, however, hydraulic properties of the minesoil would likely lead to droughty conditions and extended periods of plant stress.
Soil Genesis as Affected by Topography and Time in Highly Calcareous Parent Materials Under Semiarid Conditions in Iran
Authors: Abtahi Ali
Published: July 2010

Soil formation as affected by topography and time was studied in highly calcareous parent materials under the semiarid conditions of southern Iran. Soils of the 95,000‐ha Sarvestan basin were considered for this purpose.

Topographic features of the Sarvestan basin were related to variations in soil texture and salinity. Slightly saline, coarse‐textured soils occurred at high elevations, whereas fine‐textured soils of higher salinity occurred at low elevations. Based on salinity status, these two general soil types were classified as Inceptisols and Aridisols, respectively.

Soils comprising a chronosequence differed mainly in the redistribution and accumulation of carbonates. They ranged from those developed in Holocene alluvium (Typic Xerofluvents) and lacking any evidence of carbonate redistribution to those developed on Lower or Middle Pleistocene surfaces (provisionally classified as Petrocalcic Xerochrepts) and showing distinct petrocalcic horizons.

X‐ray and electron optical analyses indicated a clear gradation in the relative contents of palygorskite and smectite clay minerals within this chronosequence. Palygorskite increased as smectite decreased in older soils.
Alfalfa for Hydrologic Control of Saline Seeps
Authors: Halvorson A. D. , Reule C. A.
Published: July 2010

Saline seeps affect extensive dry cropland areas in the northern Great Plains and methods need to be devised to control them. The effectiveness of alfalfa (Medicago sativa L.) in controlling saline seepage on northern Great Plains small grain dryland farms was studied from 1971 to 1977.

Alfalfa, when grown on about 80% of the recharge area, reduced the deep percolation of soil water and provided hydrologic control for two seep areas within 1 year after its establishment in recharge areas. As the perched water table receded, the soil surface in the discharge (seepage) area dried allowing passage of farm implements, soil salinity decreased, and weeds, grasses, and crops grew better in the seepage area.

In contrast, a buffer strip of alfalfa (occupying about 20% of recharge area) on the upslope side of a saline seep did not provide hydrologic control. Greenhouse data indicated that alfalfa yields will decrease rapidly if soil salinity increases to high levels above a saline water table. Reduced plant growth resulted when salts accumulated in the root zone as water moved upward by capillary action. When in situ root zone soil salinity reached an EC of 38 mmho/cm, alfalfa growth essentially ceased.

We concluded that alfalfa can effectively control the hydrology of saline seep areas if it is grown on a major portion of the recharge area.
Effects of Fire on Nitrogen in Forest Floor Horizons
Authors: Mroz G. D. , Jurgensen M. F. , Harvey A. E. , Larsen M. J.
Published: July 2010

The effects of burning no nitrogen (N) losses and transformations in red pine (Pinus resinosa Ait.), eastern hemlock [Tsuga canadensis (L.) Carr.], and Douglas‐fir (Pseulotsuga menziesii)/western larch (Larix occidentalis Nutt.) forest floor were investigated. Organic horizon samples were burned at 400°C for 30 min in a top‐heating oven to simulate field conditions. Measurements taken immediately after burning showed total and available N losses from the O1 horizons but gains in total and available N in underlying layers. After burning, the litter was incubated for 5 weeks and analyzed for ammonium and nitrate concentrations and changes in acidity. Each forest floor type displayed varying patterns of ammonification, nitrification and immobilization of N. The N changes appeared related to the differing initial N contents of the organic material.
Aqueous‐ and Sediment‐Phase Nitrogen Yields from Five Southern Pine Watersheds
Authors: Schreiber J. D. , Duffy P. D. , McClurkin D. C.
Published: July 2010

Nitrogen (N) in solution and associated with suspended sediments in stormflow from five reforested watersheds (1.5–2.8 ha) in northern Mississippi was determined during the 1975 water year. Samples were collected using Coshocton wheel samplers set below 0.91‐m H‐flumes. Mean yearly solution NH4‐N and NO3‐N concentrations, 0.20 and 0.01 mg/liter, respectively, did not differ among watersheds. Sediment‐N concentrations ranged from 2,410 to 6,080 µg/g and were 5.4 to 10.0 times those in the watershed soils. The N enrichment of sediment relative to soil was attributed to selective erosion of fine sediments (clay) and/or deposition of coarse sediments in transport. Significant differences in sediment N yields among the five watersheds were related to stormflow volume, sediment concentration, and sediment N concentration. Nitrogen was transported from the watersheds about equally in the sediment and solution phases. Mean solution NH4‐N and NO3‐N yields for the water year were 422 and 28 g/ha, respectively, for the five watersheds; mean sediment N yield was 395 g/ha. For the year, 8–17% of the precipitation was measured as stormflow; the remainder was deep seepage and evapotranspiration since there was essentially no baseflow.
Compression of Agricultural Soils from Eight Soil Orders
Authors: Larson W. E. , Gupta S. C. , Useche R. A.
Published: July 2010

Compression curves (bulk density vs. log applied stress) determined on 36 world agricultural soil samples at a given water content were linear over the range of stresses from about 1 to 10 kg cm−2. Compression curves determined for soils at different water contents were approximately parallel to each other over the range of initial pore water potentials from −0.05 to −1.0 bar. The compression index, C (slope of the compression curve), increased approximately linearly as clay content of the soil increased up to about 33% and then remained approximately constant as clay content further increased. The maximum C value was 0.55 for soils with predominantly 2:1 type clays and 0.50 for soils with predominantly kaolinite or iron oxides in the clay fraction. If the compression curve at one water content is known, a procedure is suggested to predict compression curves at other water contents.
A Simulation Model for Predicting Infiltration into Cracked Clay Soil
Authors: Hoogmoed W. B. , Bouma J.
Published: July 2010

Infiltration into dry cracked clay soil was simulated by combining two existing physical simulation models for vertical and horizontal infiltration, using boundary conditions for horizontal infiltration that were defined by morphological data. Vertical flow into the cracks occurred when the application rate exceeded the calculated vertical infiltration rate of peds between cracks. Calculated horizontal infiltration from the cracks into adjacent dry peds was limited because it had to occur from a few small vertical bands along which the water moved. The contact area (S) of all bands had been determined in situ in 0.5‐m2 plots per 10‐cm depth interval using morphological staining techniques. S was a function of the applied flow regime. “Short‐circuiting,” which was defined as preferential movement of free water along large pores through unsaturated soil, was predicted well by the model. Short‐circuiting increased when the initial moisture content of the soil was higher.
The Effect of Crushed Basalt Scoria on the Cation Exchange Properties of a Highly Weathered Soil
Authors: Gillman G. P.
Published: July 2010

Soil from the surface horizon of a highly weathered soil (Acrohumox) from tropical Queensland was mixed with crushed basaltic cinders and incubated in a moist condition for 12 months in the laboratory. The cation exchange capacity (CEC) increased from 9 to 14 meq/100 g in direct relationship to the rate of application and degree of fineness of the scoria, as well as to the duration of incubation. The increase in CEC was accompanied by an increase in exchangeable calcium, magnesium, and potassium. The results suggest that crushed basaltic scoria could be successfully used to prevent cation nutrient losses from highly weathered soils of the tropics.
Measurement of Adsorption on Solids by the Axial Filter; Linear Vs. Nonlinear Isotherms
Authors: Egozy Yair
Published: July 2010

Use of the axial filter for adsorption measurements and evaluation of distribution coefficient is described. Adsorption of Sr(II), Co(II), and Cd(II) on Na montmorillonite from solutions of a wide range of NaCl concentration was measured by the axial filter and compared with results obtained by other experimental methods. Agreement was found for Sr(II) and Cd(II) systems. Disagreements between batch and axial filters results for Co(II) adsorption appear to rise mainly from the slow kinetics of the Co(II) adsorption.

Adsorption of Sr(II) on alumina was used to demonstrate the application of the axial filter method for a nonlinear isotherm case. The nonlinear isotherm, obtained by a batch method, was used to explain the behavior of the system in an axial filter experiment. Good agreement was obtained between the predicted and the experimental axial filter results.
Greenhouse Evaluation of Four Phosphorus Soil Tests in Relation to Phosphate Buffering and Labile Phosphate in Soils
Authors: Holford I. C. R.
Published: July 2010

Four soil P tests — Olsen, Colwell, Bray, and Mehlich — were evaluated in a greenhouse experiment in relation to plant uptake, relative yield, labile P, and buffer capacity on 30 soils varying in pH from 5.4 to 8.1. The Olsen and Colwell tests were most highly correlated with plant uptake, and the Olsen and Bray tests with relative yield. When the soils were stratified into weakly, moderately, and strongly buffered groups, it was found that extraction of labile P was depressed by increasing buffer capacity most in the Bray test, followed by the Olsen test, and least in the Colwell test. The Bray test tended to overcompensate for the effects of buffering on plant uptake and therefore underestimated the amount of available P in strongly buffered soils, whereas the Colwell method tended to overestimate it in strongly buffered soils. The Olsen test appeared to be correctly sensitive to buffering and therefore gave the highest correlations with both plant parameters. The Mehlich test extracted large amounts of nonlabile P in soils with pH >6.0 and was therefore weakly correlated with plant uptake and relative yield. The results showed that in a successful soil test, increasing buffer capacity will depress the extraction of labile P in the same way as it depresses uptake by plants.