bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Evaluation of Zonal Centrifugation as a Research Tool in Soil Science: I. Methodology
Authors: Francis C. W. , Bonner W. P. , Tamura Tsuneo 
Published: July 2010

AbstractThe methodology involving zonal centrifugation of clay sized mienrals through density gradients is presented. Various aspects of the procedure such as gradient solvents, formation of the gradient, dispersing agents, and methods of band removal are discussed. The parameters of centrifugal force, saturating cation, and particle size were evaluated as to their effect on time and isopycnic banding location within the gradient. It was concluded that an ultracentrifuga is required (a force field greater than 623 g) to band isopycnically clay particles of < 0.2 microns in diameter. The saturating cation influenced banding of 2:1 expandable layer silicates to a greater degree than 1:1 layer silicates, and the spatial relationshp of the expanding layer silicate associated with specific cation saturation played a larger role in banding than differences in atomic weight among the saturating catons.
Approximation of Field Hydraulic Conductivity by Laboratory Procedures on Intact Cores
Authors: Roulier M. H. , Stolzy L. H. , Letey J. , Weeks L. V. 
Published: July 2010

AbstractThe utility of several laboratory procedures for approximating field values of unsaturated hydraulic conductivity over the suction range 30 to 100 cm of water was studied. Conductivity was measured at the 68‐cm depth using neutron probe and tensiometer data taken during drainage of a bare plot of Ramona sandy loam. Conductivity was measured in the laboratory on 10‐ by 30‐cm intact cores by the transient flow (TF) method of Richards and Weeks and was calculated by both the Marshall (M) equation and Millington and Quirk (M&Q) equation using moisture characteristic curves from laboratory measurements on intact cores and from the field data.The TF values were all higher than field values but, when used with a matching factor, they satisfactorily approximated field conductivities. This study, the first test of this TF method against field data indicated that the method of calculating the flow velocity influenced the results and that the best results were obtained from a computer program which used a numerical differentiation subroutine.When used with matching factors, conductivities calculated (for 33 pore classes) by the M equation and M&Q equation were good approximations of field conductivity, though less satisfactory than results from the TF computer calculations. The best M&Q values were calculated from a field moisture characteristic while the M values were satisfactory when calculated either from the field moisture characteristic or from one measured in the laboratory on intact 6 by 10‐cm cores.It is recommended that the conductivity value to be used in calculating the matching factor for any of these methods be measured in the field within the suction range being studied.
Seepage Through Soil Bedding or a Hillside Due to a Steady Rainfall: I. Soil Surface of Constant Slope
Authors: Selim M. Sami , Kirkham Don 
Published: July 2010

AbstractA theoretical solution for the seepage of steady rainfall through soil bedding (a series of formed parallel mounds and depressions, or furrows used in land drainage when soil overlies an impermeable layer) is given. The solution considers a finite depth of water in the bedding depression or furrow. The geometry on an extended scale can be considered as that of a hillside with water seeping to a river, or, on a small scale, as that of the side of a water‐saturated ridge‐furrow combination in a row‐crop field. The solution of the problem offers a mechanism as to how soluble chemicals below the soil surface may get into overland flow. The mechanism is: the rainfall enters the soil, moves downslope in the soil and then moves upward out of the soil, carrying soluble chemicals, such as fertilizers, insecticides, etc. This upward moving soil solution merges into surface runoff.
Properties and Genesis of Selected Colombian Andosols
Authors: Calhoun F. G. , Carlisle V. W. , Luna Z C. 
Published: July 2010

AbstractA climosequence of southern Colombian Andosols developing in andesitic volcanic ash was studied through the use of physical, chemical, and mineralogical parameters in an effort to further elucidate pedogenesis of volcanic ash weathering.The four Andosol profiles were characterized by high organic carbon contents especially at higher elevation. Sodium fluoride pH values suggested that the clay fractions of these profiles were dominated by allophanic colloids. Low bulk densities and high 15‐bar H2O contents reflected the high porosity of Andosols and the hydrophilic nature of allophane, respectively.Hornblende was the dominant heavy 50‐500µ fraction mineral except in some horizons of the 3,510‐m profile which were dominated by pyroxenes. Volcanic glass decreased with profile depth and increased with increasing altitude.Varying amounts of vermiculite, hydrated halloysite, metahalloysite, cristobalite, and allophane were identified by infrared and X‐ray analyses. Hydrated halloysite, metahalloysite, and allophane were identified in the fine clay fraction.A clay mineral weathering sequence of allophane → hydrated halloysite was postulated. The maturation of this sequence increased with profile depth and with decreasing altitude. Occurrence of metahalloysite in surface horizons was attributed to periodic higher moisture tensions. It is hypothesized that coarse clay vermiculite is transient or, alternatively, that insufficient time has elapsed for its transformation to other 2:1 phyllosilicates. It is further postulated that vermiculate pedogenesis occurred rather rapidly through modification from a primary mineral source (possibly biotite).
Infiltration Rate as Affected by Soil Freezing Under Three Cover Types
Authors: Harris Alfred Ray 
Published: July 2010

AbstractInfiltration rate in a frozen Fayette silt loam soil under contiguous areas of natural deciduous forest, 25‐year‐old confierous plantation, and 6‐year‐old abandoned field vegetation was measured over the winter of 1969‐70 using tin can infiltrometers and a water‐ethylene glycol solution. The deciduous forest site had a natural soil profile; the conifer plantation and abandoned field sites were once cultivated. Prefreeze infiltration rate was similar for all cover conditions. In deciduous forest and abandoned field plots, soil freezing did not change the infiltration rate sharply until late winter when infiltrating snowmelt and rainfall froze and closed soil pores. In the conifer plantation, the infiltration rate was nearly zero in early winter due to an impermeable snow‐ice layer on the ground caused by snowmelt dripping from the conifer canopy. Because of large macropores, infiltration rates were high on the deciduous forest and abandoned field plots even when the frozen soil contained nearly 50% water by volume. Conifer plantations may thus contribute more surface run‐off than deciduous forest or abandoned fields during snowmelt and winter rains.
Spodosol Development and Nutrient Distribution Under Hydnaceae Fungal Mats
Authors: Fisher R. F. 
Published: July 2010

AbstractThe hyphae of Hydnellum scleropodium Harrison form tough, felt‐like mats at the base of the O horizon in dry jack pine (Pinus banksiana Lamb.) forests. The effects of these mats on the underlying soil were investigated in forests near Sioux Lookout, Ontario, Canada. The stands studied contained an average of 100 mats/ha. These mats were approximately 1 m in diameter and covered about 1% of the land area. The O horizon above the mats was thinner than in the adjacent area. The soil profile beneath the mats was more meature than the average profile in the area due to increased movement of organic matter, Fe, Al, and exchangeable bases downward into the B horizon. No evidence of increased clay translocation was found. In the A2 and B2 beneath the mats, total N was lower and extractable N was higher than in the surrounding soil. Both total P and extractable P were lower in the A2 and higher in the B2 beneath the mats. Extractable K was higher in the A horizon beneath the mats than it was in the normal soil. The fungal mats sped soil profile development and increased nutrient availability in the soil directly beneath them.
Mineralogical Properties of Clays from Panama Soils
Authors: Reneau, R. B. , Fiskell J. G. A. 
Published: July 2010

AbstractPanama soil clays from eight Alfisols were studied extensively by X‐ray diffraction, DTA, and infrared spectroscopy. Composition of these clays was examined before and after sequential selective dissolution with citrate‐dithionite and hot 0.5N NaOH for removal of amorphous components. Vermiculite was the dominant mineral in three clays, and smectite in four others. In one soil, a poorly crystalline mineral was present and this clay had an unusally large low‐temperature endotherm which was attributed to a combination of halloysite, an expandable phyllosilicate, and amorphous materials. In the other clays the shape of the high‐temperature endotherms indicated presence of kaolinite ranging in content from 19 to 27%. Infrared spectra showed a large absorption band of 3,450 cm‐1 for water adsorbed to clay surfaces indicating the presence of halloysite and/or 2:1 expanding phyllosilicates. Absorption bands at 910 cm‐1 found for some clays was attributed to A1‐O‐H bending presumably from halloysite. Mica content ranges from 1.4 to 12.0%. Considerable interlayer hydroxy‐A1 and hydroxy Fe appears to be present in the expanding phyllosilicates from incomplete collapse of spacings after K saturation and heating to 550C. After sequential dissolutions, and allowing for CEC of kaolinite and mica, CEC of the expanding phyllosilicate fractions ranges from 61 to 152 meq/100 g at pH 4.8 and increased about 15% more when measured at pH 8.2.
Transport Numbers and Mobilities of Ions in Bentonite Membranes
Authors: Shainberg I. , Kemper W. D. 
Published: July 2010

AbstractNa‐clay was compacted by porous barriers between solutions of different concentrations. Conductance of the clay and electrical potentials across the clay were measured and used to calculate the transference numbers for the Na ion. The transference numbers calculated from conductivity studies were higher than those calculated from emf measurements. A qualitative explanation for the lower numbers estimated from potential measurement is proposed which involves osmotically induced convective movement.
Competition Between Species During Nitrification in Soil
Authors: McLaren A. Douglas , Ardakani M. S. 
Published: July 2010

AbstractPreviously we have derived equations which describe populations of nitrifying organisms growing in an idealized soil column perfused with nutrient solutions. Population growth in the soil column at any particular depth is here discussed in terms of a kinetic model that allows for exhaustion of nutrient or space, i.e., surface area limitation, whether or not death occurs, and competition between two species in the same niche. The model in its various ramifications is subject to laboratory tests and points up inadequacies in current understanding of the microscopic ecology of nitrification.
Climosequence of Ash‐Derived Soils in the Central Cordillera of Colombia
Authors: Cortes A. , Franzmeier D. P. 
Published: July 2010

AbstractFour soils derived from volcanic ash were studied in a transect on the east slope of the Central Cordillera of Colombia. Average annual temperatures range from 8C at 3,670 m altitude to 24C at 980 m. Only the soils located in the lower part of the transect have B horizons. From highest to lowest elevation the soils are classified a Cryandept, a Humitropept, and two Dystrandepts. The sand and silt fractions of the soils consist of a similar suite of minerals, several of which are high in sodium. Volcanic glass and plagioclase are most abundant; cristobalite, quartz, vermiculite, pyroxenes, hornblende, amphibole, and magnetite are present in smaller amounts. Amorphous material predominates in the clay fraction of the soils, but crystalline minerals such as smectite, vermiculite, chloritic intergrade mineral, imogolite, halloysite, kaolinite, and some primary minerals are also present.The genesis of the soils is controlled chiefly by climate and by the nature of the parent material. As the environmental temperature increases, the degree of B horizon development increases, clay content increases, organic matter content decreases, degree of weathering of primary minerals increases, and the content of amorphous material, kaolinite, and halloysite increases.
Kinetics of Losses of PCNB and DCNA in Three California Soils
Authors: Wang C. H. , Broadbent F. E. 
Published: July 2010

AbstractThe losses of two fungicides, PCNB (pentachloronitrobenzene) and DCNA (2,6‐dichloro‐4‐nitroaniline) in three California soils differing in their properties were measured in laboratory experiments. Under controlled temperature and moisture content, both fungicides were lost according to first‐order kinetics. The calculated half‐time (t½) was employed to indicate the stability or the persistence of the fungicides. The half‐times of PCNB were found to be 4.7, 7.6, and 9.7 months for Columbia fine sandy loam, Sacramento clay, and Staten peaty muck, respectively, while those of DCNA were 30, 16.2, and 13.6 months, respectively. Thus higher soil organic matter was associated with slower PCNB loss but enhanced DCNA loss. It was also found that clay affected losses of the fungicides in a similar way. Evidence was obtained to show that PCNB was lost mainly through volatilization whereas DCNA was lost through microbial degradation and other processes.
Magnesium Forms in Selected Temperate and Tropical Soils
Authors: Mokwunye A. Uzo , Melsted S. W. 
Published: July 2010

AbstractA scheme was developed for fractionating soil Mg into exchangeable, organic‐complexed, acid‐soluble, and primary mineral forms. The scheme was tried out on 20 soils from different regions of the world. Magnesium content was influenced by the nature of the parent materials, climate, and age of the soil. There was more Mg in youthful alluvial soils from Southeast Asia as well as loess and till‐derived Illinois soils which had high amounts of 2:1 lattice clays. Highly weathered oxisols from Sierra Leone were low in Mg. In general, within the soils studied, Mg distribution ranked in the following order: Primary mineral > Acid‐soluble > Exchangeable > Organic‐complexed.Oxisols that had very low exchangeable Mg contained appreciable amounts of Mg in the form of Mg‐Al silicates of reduced solubility. Organic‐complexed Mg was very low in all the soils studied.
Reactions of DTPA Chelates of Iron, Zinc, Copper, and Manganese with Soils
Authors: Norvell W. A. , Lindsay W. L. 
Published: July 2010

AbstractThe Fe, Zn, Cu, and Mn chelates and the Na salt of DTPA (diethylenetriaminepentaacetic acid) were reacted with suspensions of acid and alkaline soils. The suspensions were aerated and shaken continuously for periods of 2 hours to 30 days. The concentrations of soluble Fe, Zn, Cu, Mn, Ca, and Mg were measured by atomic absorption spectrophotometry, and the concentration of 14C‐labeled DTPA was determined by a liquid scintillation technique.Additions of Fe‐DTPA were effective in maintaining soluble Fe in four soils ranging in pH from 5.8 to 7.3. Even at pH 7.9 more than 13% of added Fe remained soluble after 30 days of reaction in a calcareous soil. DTPA was an ineffective chelate for Zn and Cu in soils at pH 5.8 and 6.2, but became more effective with rising pH. In the alkaline soils more than 50% of added Zn and Cu remained soluble during 30 days of reaction. Essentially all Mn from Mn‐DTPA additions was lost from solution within 3 days in all soils. Discrepencies between the concentrations of 14C‐labeled DTPA and soluble micronutrient metals suggest that an appreciable fraction of 14C‐labeled DTPA decomposed to unknown products having different chelating capabilities.
Horizontal Infiltration into Layered Soils
Authors: Reichardt K. , Nielsen D. R. , Biggar J. W. 
Published: July 2010

AbstractA numerical solution of the soil water movement equation is presented for horizontal infiltration into air‐dry layered soils. The solution is based upon a scaled soil water diffusivity function common to six homogeneous soils and values of the microscopic characteristic length ascertained for each soil from homogeneous columns. Soil water content distributions and cumulative infiltration for different sequences of soil layers are analyzed. Agreement between experimental and theoretical infiltration profiles suggests a convenient means to study the influence of texture and hydraulic characteristics of different layers on the infiltration process.
The Numerical Analysis of Infiltration into Heterogeneous Porous Media
Authors: Whisler F. D. , Watson K. K. , Perrens S. J. 
Published: July 2010

AbstractPonded infiltration into a heterogeneous porous medium was studied using a numerical solution of the flow equation. The medium was assumed to exhibit scale heterogeneity, the heterogeneity being specifically defined in terms of a linear variation of the resaturated hydraulic conductivity with depth. The spatial variation of the hydrologic characteristics was initially defined in terms of the water entry value of the medium at the point in question and an empirical relationship between the water entry value and the resaturated hydraulic conductivity. Pressure head and water content profiles were obtained for two hydraulic conductivity distributions and compared with that for a homogeneous soil having an average conductivity. The profiles reveal distinct regions that are different from the uniform case depending on whether the conductivity is increasing or decreasing with depth.
Aluminum and Iron Ion Products in Acid Extracts of Samples from Various Depths in a Menfro Soil
Authors: Blanchar R. W. , Scrivner C. L. 
Published: July 2010

AbstractSamples from ten horizons of a Menfro soil were equilibrated for 16 and 65 days with dilute HCl. Aluminum, iron, and phosphorus contents and pH and E (platinum) were determined on the solution portion. The values of pAl + 3pOH, pAl + 2pOH + pH2PO4, pFe + 3pOH, and pFe + 2pOH + pH2PO4 were computed for each horizon.The aluminum hydroxide ion product was found to be pH dependent. Gibbsite shows the same pH dependence under similar conditions. Comparisons between pAl + 3pOH values of gibbsite and Menfro soil made at the same pH indicated the aluminum oxides in the Menfro soil had solubility characteristics similar to gibbsite. Values of pAl + 3pOH corrected for pH dependence were the same at all depths in the Menfro profile. The pAl + 2pOH + pH2PO4 values in the Menfro soil, although pH dependent, were similar to variscite.Iron hydroxide solubility was found to be similar to goethite. Values of pAl + 3pOH were found to be lower in the lower B and upper C horizon than in other parts of the profile. A mean value of pFe + 3pOH of 41.1 was found for iron oxides in the Menfro soils. Iron phosphates were more soluble in the lower portion of the Menfro soil. The pFe + 2pOH + pH2PO4 values in the upper horizons were greater than 35 and were near 34 in the lower horizons. These data indicate iron phosphates in the Menfro soil have solubilities similar to strengite.
Oxidation of Nitrite to Nitrate in a Soil Column
Authors: Ardakani M. S. , Rehbock J. T. , McLaren A. D. 
Published: July 2010

AbstractA previously derived model for disappearance of nitrite with depth in an open soil system was tested with an especially built column filled with a sand‐soil mixture. Apparent rate constants for nitrification increased with an increase of population of nitrifiers as was expected. Nitrifiers increased almost logistically during two months in the upper portion of the column and reached a maximum population, but numbers fluctuated below the maximum population at lower depths. A decline in population density after a maximum was reached at a lower depth is attributed to partial starvation, owing to nearly complete oxidation of nitrite in the upper regions and to oxygen depletion.
Genetic Control of Uptake and a Role of Boron in Tomato
Authors: Brown J. C. , Ambler J. E. 
Published: July 2010

AbstractDifferential uptake of B by two tomato genotypes (Lycopersicon esculentum Mill) occurred both in soil and in solution culture. Boron deficiency developed in T3238 tomato grown on seven acid soils but not on five calcareous soils. The acid soils contained less, and the alkaline soils contained more, than 0.20 ppm hot‐water‐extractable B. T3238 tomato required several times as much hot‐water‐extractable B in a soil as Rutgers. With adequate B in the growth medium for uptake, T3238 utilized the transported B as well as did Rutgers. T3238 and Rutgers tomatoes can be used as indicator plants to test B availability in soils.Boron deficiency symptoms developed in the apical meristem and in the developing leaf of T3238 tomato within 48 hours after the plants were transferred from solutions containing 0.52 mg/liter of B to those containing 0.07 mg/liter. Boron deficiency in apical meristematic tissue caused: (i) increase in cell size; (ii) nuclear enlargement; and (iii) tissue disintegration. In leaf tissue B deficiency caused: (i) necrosis and collapse of the upper epidermal and palisade cells; and (ii) accumulation of phenolic materials in these areas. Rutgers developed no deficiency symptoms under the same conditions.
Activation Analysis of Aluminum from Water Extract of Soil
Authors: Misra U. K. , Graham E. R. , Upchurch W. J. , McKown D. M. 
Published: July 2010

AbstractDetermination of low‐level Al in soil water extracts or lysimeter leachings requires a method extremely sensitive in the ppb range. 1327Al(n,γ)1328Al is rapid and convenient because it has a high cross section and a short half life. 28Al may also be produced by 1428Si(n,p)1328Al. Hence a correction must be made by determining Si colorimetrially and finding the counts due to Si from a standard graph of Si concentration vs. cpm in the channels used for Al. 38Cl was the major interfering nuclide. Chloride was removed by leaching the extracts through anion exchange resin saturated with NO3. 56Manganese becomes an interfering nuclide in samples with high Mn content. Manganese corrections may be made by spectrum stripping. Aluminum standard solution was passed through an anion exchanger. Silica and aluminum standard solutions, and the sample extracts were then activated for 1 min. The samples were allowed to decay for 3 min. Then 1 ml was counted using a NaI (Tl) detector and a multichannel gamma ray analyzer. The Al content of the samples was determined and it appears that a coefficient of variation near 3.0% would be obtainable on samples down to 0.1 ppm.
Potentiometric Titration of Sulfate in Water and Soil Extracts Using a Lead‐Mercury Amalgam Indicator Electrode
Authors: Robbins C. W. , Carter D. L. , James D. W. 
Published: July 2010

AbstractSulfate concentrations in pure solutions, drainage waters, and soil saturation extracts were determined potentiometrically using a 70% Pb and 30% Hg amalgam indicator electrode and a saturated calomel reference electrode. Adjusting all samples to pH 4.7 allowed titration to a fixed potential on an automatic titrator. Sulfate concentrations ranging from 0.2 to 10 mmole/liter were determined by this method and compared with concentration determined by a turbidimetric method. Results from the two methods did not differ significantly, but the potentiometric titration method was more precise, sensitive, and rapid.