bluuebunny/crossref_metadata_2025 huggingface dataset:
Complex Reactions of Zinc With Organic Matter Extracted From Sewage Sludge
Authors: Tan K. H. , King L. D. , Morris H. D.
Published: July 2010

The organic fraction of sewage sludge, extracted with 0.1 N NaOH and separated into low and high molecular weight fulvic fractions by Sephadex G‐50 gel filtration, was studied for its Zn‐complexing capacity by the ion‐exchange equilibrium method and infrared spectroscopy.

The number of moles of fulvic compounds complexed by 1 mole of Zn at pH 5.5 was low in the case of the high molecular weight fraction, but the low molecular weight fraction was complexed in amounts twice that stated for the high molecular weight compounds. By increasing the pH to 7.0 a 10‐fold increase in amounts of low molecular weight fractions complexed by Zn was obtained. The stability constant also increased from 1.8 (pH 5.5) to 6.8 at pH 7.0 for the low molecular weight complex compounds.

The organic preparations had infrared characteristics similar to those reported earlier for polysaccharides. A shift in OH band from 3500 to 3200 cm‐1 and a sharp increase in carboxyl stretching vibration at 1650 and 1400 cm‐1, observed in the spectrograms of the Zn‐complexes, indicated the formation of coordinate covalent bonds between OH groups and Zn and electrovalent linkages between COO‐ and Zn, respectively.

Estimation of the free energy change (ΔGr) for Zn‐complex reactions suggested at least two possibilities for stable Zn‐complex formation.
Characteristics and Classification of Three Wisconsin Histosols
Authors: Frazier B. E. , Lee G. B.
Published: July 2010

On the basis of morphology, pH, and solubility in Na4P2O7, three Wisconsin histosols were classified as (i) a Fibrist, (ii) a Hemist, and (iii) a Saprist.

Fiber content was found to be the single most useful characteristic in the classification of these Histosols, and in quantifying various stages of decomposition and soil formation in histic materials. Fibric material consisted of 70% or more fiber as determined on a gravimetric basis, using a 140 mesh sieve to separate fibrous (> 0.1 mm) from nonfibrous (< 0.1 mm) material. The fiber content of hemic material ranged from 35 to 60%; sapric material contained < 15% fiber. Sodium pyrophosphate extract color (SPEC) is a useful parameter in the characterization and classification of histic materials.

Results of other analysis showed that the carbon content of the organic fraction was highest in the Saprist and lowest in the Fibrist. Oxygen and hydrogen contents were, in general, inversely related to fiber content. Total nitrogen appeared to be dependent on botanical composition of parent plants and microbial activity of the soil; the relatively high nitrogen content of certain subsurface layers may be related to illuvial deposition of mobile, nitrogen‐containing substances. Mineral content was likely influenced by additional colluvial or eolian sediments.

Good structure was found in both surface and subsurface layers of the Saprist. It is suggested that highly decomposed Saprists possessing good structure in surface and subsoil horizons be placed in a separate great group.
Hydraulic Properties of an Ortstein Horizon
Authors: Lambert J. L. , Hole F. D.
Published: July 2010

An ortstein horizon was encountered in a soil profile identified as a Wallace loamy sand on the glacial outwash plains of central Wisconsin. The horizon was distinguished by its color, strength properties, free iron concentrations, and bulk density. Laboratory and in situ field measurements of capillary conductivity indicated that the horizon was more permeable than the profile above it during wet conditions, and that it became less permeable than adjacent horizons as the soil dried out. Water retention of this ortstein horizon was greater than the rest of the profile by as much as 40%. The greatest differences in hydraulic properties were associated with the layer of maximum bulk density, while the maximum iron concentrations were observed at a slightly lesser depth.
Phosphorus Fixation by Montmorillonite and Vermiculite Clays as Influenced by pH and Soluble Aluminum
Authors: Hall J. K. , Baker D. E.
Published: July 2010

Phosphorus fixation in montmorillonite and vermiculite clays, each with a cation exchange capacity of 116 meq/100 g, was studied at various levels of Al, P and pH. Aluminum was added at rates of 0, 22.5, 45 and 90 meq/100 g to the H‐saturated clays. The clays were adjusted and equilibrated to pH levels of 4, 5, 6, and 7 prior to the addition of P at rates of 0, 200, 400, 800 and 1,600 ppm. After 14 days, a standard amount of 32P was added to each sample in order to obtain a measure of labile P by isotopic dilution. X‐ray patterns of the clays were obtained for each sample after drying at 25, 200, 300, and 550C.

Montmorillonite fixed increasing amounts of P as the pH increased, while vermiculite fixed less P as the pH increased. The fixed fraction in montmorillonite was characterized by a greater percentage of labile P than that associated with vermiculite. Stable 14 angström basal (001) spacings were detected in vermiculite at 300 C indicating the presence of stable Alpolymers within the interlayer spaces. No evidence of stable interlayer Al polymers was detected in the montmorillonite suspensions. The results help explain why the effect of liming on P availability is not the same for all soils. For soils containing clays that react like the vermiculite of this study, additions of lime prior to adding P will reduce the reactivity of Al through the formation of stable interlayer Al polymers which effectively reduces the specific surface of reactive Al and P adsorption sites. Additions of lime to soils containing clays that react like the montmorillonite of this study would increase P fixation. However, increased fixation by montmorillonite might not be associated with decreased uptake of P by plants since the latter has been shown to increase as the amounts of labile P increases.
Losses of Nitrogen from Some Flooded Soils in Tracer Experiments
Authors: Broadbent F. E. , Tusneem M. E.
Published: July 2010

Nitrogen losses were measured in laboratory and greenhouse experiments in four flooded soils after addition of 15N‐tagged (NH4)2SO4 or rice straw after various incubation periods. Substantial losses occurred in all cases except where NH4+‐N was rapidly immobilized and/or fixed by clay minerals. The necessity for nitrification as a prelude to N loss was demonstrated by showing that no loss occurred when oxygen was excluded and that where no nitrate was produced, no N2 was evolved. Growing rice plants (Oryza sativa) effectively reduced the magnitude of the nitrogen loss.
Reactions and Availability of Banded Polyphosphate in Field Studies
Authors: Miner Gordon , Kamprath Eugene
Published: July 2010

The concentration of fertilizer P from both superphosphate and polyphosphate decreased rapidly with increasing lateral distance from the band. Aluminum phosphate and lesser amounts of Fe phosphates were the soil reaction products formed with essentially no difference between the two P materials. A higher proportion of the condensed phosphate ions were in the difficultly extractable form as compared with the orthophosphate ions, indicating that the condensed phosphate ions are held more strongly. The apparent hydrolysis of condensed phosphates increased with increasing lateral distance from the center of the band. Hydrolysis was greater in the Lynchburg, a low P‐fixing soil, than in the Georgeville, a high P‐fixing soil.

Polyphosphate was as effective as superphosphate in supplying P for plant growth. The residual effectiveness of the polyphosphate was similar to that for superphosphate. Although condensed phosphate ions are held more strongly than orthophosphate by soil materials, there appears to be no difference in their effectiveness as sources of P for plants.
Effect of Soil pH on the Availability of Adsorbed Sulfate
Authors: Elkins D. M. , Ensminger L. E.
Published: July 2010

A soil solution displacement method was used to evaluate the effect of CaCO3 on soil retention of sulfate. A decreased amount of sulfate retention was noted with increased rates of CaCO3.

By means of a split‐root technique, plants of soybeans (Clycine max (L.) Merrill) and cotton (Gossypium hirsutum L.) were grown in a Dothan subsoil which contained a large amount of adsorbed sulfate, and to which had been added several rates of CaCO3. As CaCO3 rate was increased the uptake of sulfate by five crops of soybeans and one crop of cotton grown successively in the same soil was generally greater. A portion of the adsorbed sulfate in the untreated soil was available, but available sulfate became limiting for the third crop of soybeans and for all successive crops of soybeans and cotton.
Comparison of Different Methods in the Transition Matrix Approach to the Numerical Classification of Soil Profiles
Authors: Norris J. M.
Published: July 2010

Dale et al. (1970) have proposed a method for the numerical classification of sequences which was used by Norris and Dale (1971) for the classification of soil profiles. In the first stage the horizons from all the profiles are grouped and the profiles redescribed as a sequence of groups. In the second stage the sequences are classified by the program TRANSMAT. This paper examines the effect of using different first stage methods, different numbers of groups at the end of the first stage and methods similar to TRANSMAT in the second stage. Both the first stage method and the number of groups used bear significantly on the results. However, alternative techniques to TRANSMAT can be used with little loss of precision but with greatly increased data storage capacity.
Diffusion of Zinc in Soil: II. The Influence of Soil Bulk Density and its Interaction with Soil Moisture
Authors: Warncke D. D. , Barber S. A.
Published: July 2010

Effective Zn diffusion coefficients were determined at four soil bulk densities and three moisture levels in five silt loam soils. The tortuosity of the diffusion path, f1, for each set of soil conditions was estimated from 36Cl diffusion data. In each soil and for each soil moisture level the diffusion path was least tortuous near 1.3 g/cm3. The observed order for the influence of soil bulk density on tortuosity was 1.6 > 1.5 > 1.1 > 1.3 g/cm3. Soil bulk density interacted significantly with soil moisture in affecting the Zn diffusion coefficients. The maximum rate of Zn diffusion did not always occur at a soil bulk density of 1.3 g/cm3 where the diffusion path was least tortuous. At 20 and 30% moisture the Zn diffusion rate reached a maximum near 1.5 g/cm3 indicating that tortuosity was not the only factor influencing the rate of Zn diffusion. As the soil moisture was increased, a reduction in the effect of the interaction of Zn with the soil was greater than the effect of tortuosity in determining the effective rate of Zn diffusion in each soil. When the bulk density was increased from 1.5 to 1.6 g/cm3, an increase in both the degree of interaction and toruosity combined to cause a sharp decrease in the Zn diffusion coefficient.
Phosphorus Diffusion in Soils: II. The Effect on Phosphorus Uptake by Plants
Authors: Mahtab S. K. , Swoboda A. R. , Godfrey C. L. , Thomas G. W.
Published: July 2010

Phosphorus uptake by grain sorghum (Sorghum vulgare) was measured at four levels of applied P and three levels of moisture on four related Texas soils. The soils differed mainly in clay content. Phosphorus uptake was found to be a function of clay and water content of the soils and applied P. The total increase in dry matter yield for each addition of P was about the same for each soil except at the lowest moisture level. At the lower moisture levels, response to P additions was not as great on the coarser‐textured soils as on the fine‐textured soils.

Phosphorus uptake was related to the diffusion coefficients of P previously determined for the four soils subjected to the same treatments as in this study; the correlation coefficient was 0.788.
The Composition of the Soil Atmosphere Beneath a Beef Cattle Feedlot and a Cropped Field
Authors: Elliott L. F. , McCalla T. M.
Published: July 2010

The soil gases beneath a feedlot and an adjacent cropped field were measured at several time intervals and soil depths for a 1‐year period. The gas samples were obtained in situ with gas diffusion equipment protected by caissons installed in the feedlot and field.

During warm periods and when the feedlot was not unusually dry, average concentrations of up to 51.5% CH4 and 35.5% CO2 were detected in the feedlot soil profile atmosphere. Methane and CO2 feedlot values for the year averaged from 8–27.5% and 12.5–23%, respectively. When CH4 and CO2 values were high, O2 concentrations were minimal. High CH4 values were recorded up to 152 cm deep in the feedlot. No H2 was detected beneath the feedlot or the cropped field. Oxygen and CO2 values ranged from 12.5–21% and 0.1–5%, respectively, in the cropped field soil profile. No CH4 was detected.

Methane and CO2 concentrations beneath the feedlot were lowest in midwinter and during extended drought periods in early summer; O2 concentrations were highest during these periods. The cropped field soil profile showed the highest CO2 values in the summer when the crop was growing vigorously; O2 values were lowest during this period.
Characterization of Aluminum in Volcanic Ash Soils
Authors: Igue K. , Fuentes R.
Published: July 2010

Buffered and unbuffered salt solutions were used to characterize Al in acid volcanic ash soils of Costa Rica. The results presented show that the exchangeable Al in the Andosols studied are relatively low as determined by successive extractions with unbuffered salt solutions. When different soils were compared, exchangeable Al seemed to increase as weathering of the soils increased. Buffered 1N NH4OAc at low pH's releases considerable amounts of nonexchangeable Al. In a well developed Andosol, part of nonexchangeable Al seems to be released from organically complexed forms. In more weathered soils, the inorganic forms of Al seemed to be the main source of nonexchangeable fractions.

The method of successive extractions with unbuffered salt solutions appeared to provide a reliable measuremnt of exchangeable and nonexchangeable Al. Both 1N KCl and 1N NH4Cl generally extracted similar amounts of Al from soils, and both methods are very sensitive to detect differences due to lime treatments or organic matter destruction.
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

The 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

The 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

A 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

A 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

Infiltration 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

The 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

Panama 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

Na‐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

Previously 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

Four 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

The 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

A 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

The 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

A 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

Ponded 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

Samples 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.
Saturated Water Flow Through Clay Pots
Authors: Spomer L. Arthur
Published: July 2010

Saturated water flow through soil‐filled, standard clay pots draining into the atomosphere was simulated for flood and drip irrigation by an electrolytic tank electric analog. Simulated flow patterns indicated significant zones of low flow rates, particularly during drip irrigation. The significance of these flow patterns to crop growth was not determined.
Oxidation of Nitrite to Nitrate in a Soil Column
Authors: Ardakani M. S. , Rehbock J. T. , McLaren A. D.
Published: July 2010

A 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

Differential 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

Determination 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

Sulfate 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.
Effect of Flooding on the Eh, pH, and Concentrations of Fe and Mn in Several Manitoba Soils
Authors: Olomu M. O. , Racz G. J. , Cho C. M.
Published: July 2010

The changes in Eh, pH, and concentrations of Fe and Mn in the solutions extracted from six Manitoba soils saturated with water were studied at various times of incubation at room temperature. Gradual reduction of the extracts was observed during the first 3 to 4 weeks of incubation. After this period, the extracts, in many instances, gradually returned to relatively oxidized states with occasional reduction. Somes changes in pH were observed but the magnitude of change was relatively small in soils with a relatively high cation exchange capacity. Both Fe and Mn concentrations generally increased with increased reduction. This trend was more pronounced for Mn than for Fe.

E0 values calculated from experimentally measured Eh, pH, and concentrations of Mn appeared to indicate the presence of the Mn2O3 − Mn2+ redox system. The calculated values of E0 based on the assumption that the Fe2O3 − Fe2+ redox system was operative were far greater than the theoretical value.

Almost all the Fe in soil solution was complexed with organic matter whereas Mn was either not complexed or only weakly complexed. The metal‐organic matter complexes were negatively charged. The soil solutions had a greater affinity for Fe than did 10‐4M EDTA. It is suggested that the very high degree of complexing of Fe in soil solution was most probably responsible for failure to obtain the theoretical E0 values for the Fe2O3 — Fe2+ redox system from the experimental data.
Factors Affecting the Coefficient of Linear Extensibility in Vertisols
Authors: Anderson J. U. , Fadul Kamal Elfadil , O'Connor G. A.
Published: July 2010

The relationship of the coefficient of linear extensibility (COLE) to other soil parameters was studied in 16 horizon samples from Ustert and Torrert profiles from the Sudan, Arizona, and New Mexico. The soil parameters studied were: percent of fine clay, coarse clay, silt, organic carbon, inorganic carbon, and EC × 103 and ESP. COLE was highly correlated with fine clay percentage and ESP, yielding a multiple correlation coefficient (R2) of 0.938. The R2 value for fine clay only was 0.868. X‐ray diffraction patterns indicate that the mineralogy of the fine clay ranges from dominantly well‐crystallized montmorillonite to poorly‐crystallized montmorillonite plus amorphous material. A predictive model which assumes that these Vertisols expand because of changes in basal spacings of fine clay, and that external expansion does not occur until voids are filled yields results which are highly correlated with measured COLE.
A Batch‐Handling Technique for Hot‐Water Extraction of Boron from Soils
Authors: John Matt K.
Published: July 2010

A procedure was developed for the extrraction of boron by hot‐water. The method was suitable for a large number of samples and a high degree of accuracy was obtained. The proposed procedure was compared with the reflux and Gupta's modified methods by using three soils of varying texture and organic matter. The reproducibility of the proposed method was found to be superior to that of the others. The apparatus should improve the sample handling efficiency for a variety of extraction procedures that require hot solvents.
Solution Phosphorus Concentration and Growth of Rice (Oryza sativa L.) in Flooded Soils
Authors: Hossner L. R. , Freeouf J. A. , Folsom B. L.
Published: July 2010

Soil solution P concentration was monitored at weekly intervals during the vegetative growth of Rice (Oryza sativa L. var. ‘Bluebelle’) on flooded soils from the gulf coast region of Texas. Significant increases in dry matter production were obtained from application of phosphate fertilizer. Average soil solution P concentration ranged from 0.02 to 5.28 ppm when all soils and P fertilization rates were considered. A linear relationship was obtained between the logarithm of the average soil solution P concentration and the P concentration or P uptake of the plant. Yields were greater than 90% of maximum when the average soil solution P concentration was greater than 0.1 ppm. The concentration of P in the plant tissue at 0.1 ppm soil solution P was 0.25%.
Effect of Soil, Cover, Slope, and Rainfall Factors on Soil and Phosphorus Movement Under Simulated Rainfall Conditions
Authors: Munn D. A. , McLean E. O. , Ramirez A. , Logan T. J.
Published: July 2010

Three soils were treated with phosphorus at 25, 125, and 625 µg P/g soil in bare and cropped microplots and subjected to simulated rainfall. Five combinations of rainfall intensity and duration and microplot slope were used. Movement of soil and phosphorus from the microplots was measured. The quantity of runoff water, eroded solids, and P in the runoff increased with degree of slope and rainfall intensity. A high correlation (r = 0.997) was found between total P in the runoff from the bare plots and the quantity of soil eroded. Concentrations of soluble P in runoff from the plots was sufficient to eutrophy empounded water. The soil was nearly saturated with water and the system was “closed” so that runoff and leachate from a given rain were inversely related. Hence, the plant cover which was very effective in reducing runoff volume and soil erosion (as well as P losses) increased the quantity of percolating water. The increased percolation of water increased the P leached from cropped plots having uniformly mixed P. A well aggregated silty clay soil (Toledo) exhibited more infiltration than coarser textured soils with less granular structure.

A modified Chang and Jackson fractionation of the sediments showed the dominant P fractions and their increases with rate of P application to be directly related to extractable Fe and Al content, pH, and percentage base saturation of the original soils. There was no significant change in the amount of P in organic form with rate of P application.

While considerable caution must be used in extrapolating results of this kind to field conditions, the simulated rainfall and microplot method may prove useful in the study of nutrient movement by erosion and leaching under specified conditions.
Predicting Optimum Depth of Profile Modification by Deep Plowing for Improving Saline‐Sodic Soils
Authors: Rasmussen W. W. , McNeal B. L.
Published: July 2010

A previously developed procedure for predicting the effect of mixed‐salt solutions on soil hydraulic conductivity (HC) was used to predict the relative hydraulic conductivity (RHC) of separate soil horizons from saline‐sodic soils, using a standard low‐salt solution following a standard high‐salt solution at a fixed exchangeable‐sodium level. These values were then used to predict the RHC of mixtures of the same horizons simulating profiles modified to various depths by deep plowing. Weighting RHC values for individual horizons by the depth fraction of each horizon in the soil mixture provided RHC values of proper magnitude, except when large proportions of calcareous subsolum material were incorporated into the mixture. Results were improved by multiplying calculated RHC values for each soil mixture by the initial HC of the mixture. This corrected for the filling of conducting pores in more permeable horizons by smaller particles from less permeable horizons during the mixing process (analogous to particle dispersion and pore sealing during the leaching of saline‐sodic soils). Soil constants determined for the mixed soils permit the prediction of the response of these soils to any other exchangeable sodium levels or soil solution concentrations of interest. Results were consistent with lysimeter and field plot observations on the same soils, including deep plowing trials.
Yield‐Nutrient Concentration Relationships in Slash and Loblolly Pine Seedlings
Authors: Terman G. L. , Bengtson G. W.
Published: July 2010

Relationships between dry matter yields and concentrations of P and K were studied in slash pine (Pinus elliottii Engelm.) and loblolly pine (Pinus taeda L.) seedlings grown in greenhouse pot experiments comparing fertilizer rates and sources. The purpose was to determine if minimum and critical nutrient concentrations in pines could be determined more accurately in pot experiments than from field sampling or from very short‐term solution or sand culture studies.

Growth of these species of pine seedlings for 6 to 12 months was found necessary to establish minimum plant P and K concentrations. Values which permitted continuing growth of slash and loblolly pines were about 0.07% P and 0.10% K, which were essentially the same in both the needles and the entire tops of 6‐ to 8‐month‐old seedlings. Concentrations of N, P, and Ca in seedlings for which growth was not limited by these nutrients were higher in needles than in the entire tops. Critical concentrations could not be established accurately from the results obtained.
Computer Procedure for Calculating Counter‐Diffusion Coefficients
Authors: Fuqua B. D. , Dunn J. E. , Brown D. A.
Published: July 2010

A procedure for computer calculation of counter‐diffusion coefficients has been combined with the quick‐freeze technique to measure counter‐diffusion of ions. Two separate programs were employed to evaluate the counter‐diffusion coefficients at 0.1‐cm increments along the diffusion axis. Subroutines were available in the programs for plotting the ion distribution curve and the relationships of counter‐diffusion coefficients versus diffusion distance and counter‐diffusion coefficients versus relative concentration. Examples of Sr2+ diffusing against H+ and Na+ diffusing against H+ are presented to illustrate the potentialities for computer calculation and plotting of significant diffusion parameters. The diffusion coefficients of both Sr2+ and Na+ varied with changes in the ionic concentrations indicative of counter‐diffusion processes. The counter‐diffusion coefficients determined by the computer procedure were essentially the same as the values calculated by the graphical method. The computer procedure is an accurate and rapid method for calculating diffusion coefficients which are dependent on concentration and is adaptable to both single and multi‐ion systems.