bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron Spin Resonance Investigation of Mn2+ Complexation in Natural and Synthetic Organics
Authors: McBride M. B.
Published: July 2010

Mechanisms of Mn2+ bonding in soil organics and pure organic compounds were compared by using electron spin resonance (ESR) spectroscopy. The observation that Mn2+ in lower‐than‐cubic symmetry produces a very broad signal was used to quantitatively determine the degree of metal complexation by organics. As the pH was raised, multiligand molecules such as carboxymethylcellulose, citrate, and succinate formed complexes with Mn2+ as shown by a decrease of ESR signal intensity. However, monocarboxylic acids such as benzoate and salicylate do not readily form complexes with Mn2+. A fulvic acid extracted from acid soil possessed a very limited number of strong complexation sites which became available to Mn2+ only at pH values > 6.0. Polycarboxylic acids, including natural organics (peat, humic acid) and synthetic polymers (polymethacrylate, polygalacturonic acid) bond Mn2+ electrostatically as the hydrated ion at low pH, but complex increasing amounts of Mn2+ as the pH is raised. A comparison of the ESR characteristics of Mn2+ bound to soluble carboxylic acids, polymeric carboxylic acids, and strong acid compounds such as sulfonate resin is used to characterize the bonding behavior of Mn2+ in soil organics. The cooperative effort of several surface functional groups appears to be necessary to cause Mn2+ to form an inner‐sphere complex with organic solids. Higher temperatures generally favor the complexation of Mn2+.
Table Beet Yield and Boron Deficiency as Influenced by Lime, Nitrogen, and Boron
Authors: Hemphill Delbert D. , Weber Michael S. , Jackson Thomas L.
Published: July 2010

Yield, occurrence of root canker (B deficiency), and leaf nutrient concentrations of the Morse strain of ‘Detroit Dark Red’ table beet (Beta vulgaris L.) as influenced by combinations of lime and N, B, and P fertilizers were evaluated in three studies. Greatest total yields and most favorable distribution of root sizes for processing occurred with 280 kg N/ha and at soil pH of 6.6. Boron and P did not affect yield but B application reduced incidence of root canker. High rates of N application also reduced canker even though the production of large roots, which are more susceptible to canker, was increased by high rates of N. In the presence of soil‐applied B, high rates of N increased beet leaf B concentration. Application of lime tended to decrease leaf B concentration but increased canker incidence only in the absence of applied B. Liming increased P and decreased Mn concentration of leaves. The yield response to lime application may be attributed in part to reduction of Mn toxicity.
Availability of 15N‐Labeled Nitrogen in Fertilizer and in Wheat Straw to Wheat in Tilled and No‐Till Soil
Authors: Fredrickson J. K. , Koehler F. E. , Cheng H. H.
Published: July 2010

In a field study, wheat (Triticum aestivum L.) was grown in microplots under conventional tillage and no‐till seedings to compare availability of fertilizer nitrogen for two consecutive crops. The 15N‐labeled ammonium sulfate was surface‐applied in May 1980 to a spring wheat crop which utilized 25 to 40% of the fertilizer N, with the highest uptake occurring on no‐till. There was no difference in dry matter production between tillage methods. A winter wheat crop was then grown in the same microplots to assess the availability of the residual labeled fertilizer N, and in new microplots which were treated with the spring wheat straw containing 5.29 atom % 15N and 1.20% total N to assess the availability of straw N. Approximately 9% of the wheat straw N was taken up by the 1980 to 1981 winter wheat crop, while an average of 6% of the residual fertilizer N was utilized. Winter wheat dry matter production was highest on no‐till receiving 168 kg N/ha, but no difference was found between the effects of tillage methods on the availability of straw N or on the uptake of residual fertilizer N. Therefore, decreased wheat production on no‐till in the Pacific Northwest would not likely result from poorer crop utilization of fertilizer N under no‐till than under conventional tillage. Overall low crop N‐use efficiencies of the surface‐applied fertilizer N were likely due to immobilization and denitrification.
Properties and Classification of Kitsap Soils in Northwestern Washington
Authors: Shovic H. F. , Frazier B. E. , Gilkeson R. A.
Published: July 2010

The Kitsap series is widely distributed in the Puget Sound Lowlands. It has developed in glaciolacustrine sediments under the influence of cool, wet winters and warm, dry summers. This series is a benchmark soil and it has been classified as prime land for agriculture and forestry in Washington. Fourteen sites, representing the geographic range of this series, were characterized in the field. Four pedons were selected from characterization in the laboratory. A typical pedon which represents the central concept of the Kitsap series is described. The range of chemical and physical properties, genesis, and classification are discussed.

Kitsap soils occupy intermediate terraces in major stream drainages and along some bluffs facing Puget Sound. The two most important soil‐forming processes are the accumulation of organic matter and the transformations and redistribution of iron. These processes yield a thick, but relatively light‐colored epipedon, concretions, mottles, and durable aggregates. The clay fraction is dominantly vermiculite with extensive Al‐hydroxy interlayers. Laboratory and field characterization data support the placement of these soils in Aquic Xerochrepts. However, at the family level the data indicate that these soils as they are currently mapped fit (i) fine, mixed, mesic, (ii) fine‐silty, mixed, mesic, and (iii) fine, vermiculitic, mesic.
A Method for Measuring Oxygen and Carbon Dioxide in Soil
Authors: Cary J. W. , Holder C.
Published: July 2010

A simple rubber membrane gas sampling device is described for measuring soil oxygen and carbon dioxide levels. The O2 measurements are compared to results from the Pt electrode method and found to show similar trends when soil respiration was low. The membrane sensor samples a larger volume of soil and so its results have lesser coefficients of variation than do oxygen diffusion rate (ODR) measurements with Pt electrodes.
Estimating the Soil Heat Flux from Observations of Soil Temperature Near the Surface
Authors: Horton R. , Wierenga P. J.
Published: July 2010

A method was described for estimating soil heat flux by measuring soil moisture content and soil temperature at two or three depths near the soil surface. The method utilizes an analytical expression of heat flux for a semi‐infinite homogeneous soil profile for which the surface temperature is described by a Fourier series. For relatively homogeneous soil, the estimates of soil heat flux, based on observation of temperature at two depths, compared well with values of heat flux determined with the temperature integral method. Estimates were best when one of the measurement depths was very near the surface (≤ 1 cm) and the other between the 10‐ and 20‐cm depths. When soil profiles were nonhomogeneous it was found that three rather than two depths of temperature observation should be considered. Although the analytical solution for estimating the heat flux strictly does not apply to nonhomogeneous soils, heat flux values obtained with the proposed method compared favorably with those computed with the temperature integral method.
Use of an Internal Standard with Differential X‐ray Diffraction Analysis for Iron Oxides
Authors: Bryant R. B. , Curi N. , Roth C. B. , Franzmeier D. P.
Published: July 2010

In the differential x‐ray diffraction (DXRD) method the diffraction pattern for iron minerals in a soil or clay sample is obtained by subtracting the pattern for a sample free of iron oxides, after appropriate adjustment of intensity, from that of an untreated sample. We modified this method by using 1 µm α‐alumina as an internal standard to calculate the scale factor for the adjustment of intensity. The internal standard also serves as a reference for making corrections in peak position. Alumina has the advantages that it is not attacked by the citrate‐bicarbonate‐dithionite (CBD) treatment to remove iron oxides and its peak positions do not overlap the broad diffraction peaks of Fe oxides in the range of 2 to . The effects of CBD treatment on soil components other than Fe oxides can also be observed. Iron minerals in 11 soils from Indiana and Goias State, Brazil, were characterized using this technique. Hematitegoethite ratios, mean crystallite dimension, and amount of Al substitution in the iron oxides were calculated from the position, height, and width at half‐height of the DXRD peaks. The redder soils had more extractable Fe and larger hematite‐goethite ratios than the yellower soils. The amount of Al substitution in goethite and hematite and the mean crystallite dimension of hematite was greater for the Oxisols of Brazil than the Alfisols of Indiana. Maghemite was detected in soil clay of a red Oxisol from Brazil.
Fluorite Solubility in Limed Acid Sandy Soils
Authors: Street J. J. , Elwali A. M. O.
Published: July 2010

The solubility of fluorite (CaF2) in acid sandy soils was investigated via Ca2+ and F‐ activity measurements. Fluorite was added to three acid sandy soils previously limed to various pHs between 4.0 and 7.8. The equilibrium Ca2+ and F‐ activities in soil water suspensions were determined and compared to published and calculated ion activity products. The data indicated that CaF2 was the solid phase controlling F‐ activity in the suspension pH range of 5.5 to 7.0. However, below pH 5.0, the F‐ activity indicated supersaturation with respect to CaF2. The pKap for CaF2 prepared in the laboratory was calculated to be 10.50. The results revealed that liming fluoride‐contaminated acid sandy soils may reduce F‐ in the soil solution by precipitation of CaF2.
Nitrate Formation in Acid Forest Soils from the Adirondacks
Authors: Klein Theodore M. , Kreitinger Joseph P. , Alexander Martin
Published: July 2010

Nitrate formation in three forest soils from the Adirondacks region of New York was studied in the laboratory. The organic and surface mineral layers of the soils had pH values ranging from 3.6 to 4.1. Nitrate was formed when the soils were treated with artificial rain at pH 3.5, 4.1, or 5.6. Compared to simulated rain at pH 5.6, simulated rain at pH 3.5 enhanced nitrate formation in one soil and inhibited it in two other soils. The rate of nitrate accumulation was about 10 times higher in the organic horizon than in the mineral horizon, and nitrate formation was not enhanced by ammonium additions. Nitrate formation in soil suspensions was dependent on the amount of soil in the suspension, and none was formed if little soil was present. Ammonium did not enhance nitrate production in the suspensions. It is suggested that nitrate formation in these acid soils is not limited by the ammonium supply.
The Effect of Liming and Leaching on the Sulfur‐Supplying Capacity of Soils
Authors: Korentajer Leonid , Byrnes Bernard H. , Hellums Deborah T.
Published: July 2010

A greenhouse experiment was conducted to evaluate the effect of liming and subsequent percolation on SO2‐4 leaching from two soils differing substantially in their native soil S status. Two crops of corn (Zea mays L.) were then grown on the limed and leached soils with gypsum added in order to assess S crop response. With no liming, SO2‐4 leaching losses in both soils were approximately 50% of those obtained at the highest liming rates (2.0–2.5 g/kg); however, the effect varied depending on the soil S status. In the soil with the higher level of adsorbed SO2‐4 (35 µg/g of S), large losses were observed, particularly during the initial leaching period. In contrast, with the soil with the lower level of adsorbed SO2‐4 (9 µg/g of S), the leaching losses were more gradual, and SO2‐4 elution followed a chromatographic pattern commonly observed with nonsorbing ions. Possible explanations for these patterns are presented. Crop production and S uptake, particularly by the second crop, reflected the significant effects of liming and leaching on the available S status of the soils. The results indicate that acid soils that are limed and subsequently leached may rapidly become S deficient and that the relative amounts of adsorbed SO2‐4 and mineralizable S are important factors in determining the magnitude of the liming effect.
Loessial Deposits and Soils of the Snake and Tributary River Valleys of Wyoming and Eastern Idaho
Authors: Glenn W. R. , Nettleton W. D. , Fowkes C. J. , Daniels D. M.
Published: July 2010

Loess mantles hilly uplands along rivers in Star Valley and Jackson Hole in western Wyoming and Teton County in eastern Idaho. Mineralogy of the loess is relatively uniform from pedon to pedon and its particle size is relatively uniform with depth. Thickness and particle size of the loess relative to distance from the Salt River in Star Valley show that the local flood plain was its probable source. In Jackson Hole, although the mineralogy of the loess is similiar to that in Idaho, its particle size suggests that it was carried by periglacial winds which came down over outwash plains and alluvium in the north and moved south through the valley. The refractive index of glass shards in the loess is < 1.505 suggesting that the shards are from Glacier Peak, thus adding support to a late Wisconsin Age for the loess.
Genesis of a Vertisol and an Associated Mollisol in Northern Utah
Authors: Graham R. C. , Southard A. R.
Published: July 2010

The genetic relationship between a Vertisol (Chromoxerert) and an associated Mollisol with an argillic horizon (Palexeroll) was investigated. These soils occur in the Wasatch Mountains of northern Utah and have similar parent materials, altitudes, and slope gradients. Erosion is prevalent on the Vertisols because the wyethia (Wyethia amplexicaulis) plant community does not adequately cover the soil surface during the wet season of fall through early spring. Dense stands of Gambel oak (Quercus gambelii) and a continuous O horizon on the Mollisols protect them from erosion.

The Mollisol subsoil and the Vertisol solum both had cracks, slick‐ensides, high clay contents, high coefficient of linear extensibility (COLE) values, and smectite as the dominant clay mineral. These characteristics of high shrink‐swell activity were most strongly expressed in the Vertisol. The Mollisol subsoil clay was overlain abruptly by a loam surface soil. The textural difference was attributed to lessivage, in‐situ clay formation in the subsoil, and eolian contributions mixed with pre‐existing surface soil by soil animals. Eolian additions were inferred from the presence of easily weathered silt and clay‐size minerals in the Mollisol A horizons and within the zone of mixing in the Vertisol. These minerals were not present or were less abundant in the Mollisol subsoil and the Vertisol C horizon. The formation of these Vertisols was probably initiated when erosion removed the A horizons of the Mollisols, or their precursors, exposing the cracking, clayey argillic horizons at the surface.

Modification of vertic subgroup criteria to include all soils with significant shrink‐swell activity in subsoils close to the surface, regardless of surface cracking, is recommended.
The Influence of Forest and Pasture on the Genesis of a Humid Temperate‐Region Ultisol
Authors: Daniels W. Lee , Amos D. F. , Baker J. C.
Published: July 2010

The influence of pasture vs. forest vegetation on the properties of a Typic Hapludult from the Blue Ridge Province of Virginia was examined. Three study sites containing both forest and pasture cover were chosen from a group of 20 randomly selected initial sites by a typical pedon computer program which used A horizon thickness, Bt horizon clay content, Ca + Mg content at a depth of 145 cm, and slope as selection parameters. Detailed soil analyses were conducted under pasture and forest vegetation at each of the three final study sites. Pasture B horizons were deeper, higher in clay content, and weaker in structure grade than forest B horizons. The influence of liming was pronounced in the pasture soils and resulted in significant downward movement of Ca and Mg over time. Residual liming and P fertilization effects were apparent after 25 years of forest occupancy on a formerly cropped site. These data indicate that morphological and chemical changes occur in these soils following forest to pasture conversion. These changes, particularly in B horizon morphology, may occur much more rapidly than commonly assumed.
Interlaboratory Comparison of Soil Characterization Data—North Central States
Authors: Rust R. H. , Fenton T. E.
Published: July 2010

In a study initiated in 1977, eight laboratories representing experiment stations of the North Central Region plus the USDA‐SCS National Soil Survey Laboratory determined some of the most common soil properties used for classification and other purposes. Ten horizon samples were selected from soils throughout the region with the intent to include a variety of differences in physical and chemical properties. Estimates of the standard deviation from the mean of physical and chemical properties were derived. There were no significant differences among laboratories in the determination of Ca, Na, base saturation, available P, and CaCO3 equivalent but there were significant differences in determination of Mg, K, H, cation exchange capacity, organic carbon, and pH in water and in CaCl2. These differences suggest that uniformity in procedures among laboratories must be emphasized.
A New Plant Growth Technique for the Most‐Probable‐Number Estimation of Rhizobium
Authors: Garvin S. , Lindemann W. C.
Published: July 2010

A new system for growing plants in the most‐probable‐number (MPN) estimation of Rhizobium is described. Beans, peanuts, and alfalfa were grown in small plastic cone‐tainers and inoculated with suspensions of rhizobia. The number of rhizobia in pure culture, inoculants, and soil was satisfactorily estimated using cone‐tainers for host plant growth. Most‐probable‐number counts of R. phaseoli were comparable in growth pouches and cone‐tainers. The cone‐tainer system saves bench space and costs less than other presently used techniques.
Sodium Hypochlorite Methods for Extracting Microelements Associated with Soil Organic Matter
Authors: Shuman L. M.
Published: July 2010

Since hydrogen peroxide (H2O2) and sodium pyrophosphate (Na4P2O7) dissolve portions of the manganese and iron oxide fractions, respectively, sodium hypochlorite (NaOCl) was studied as an alternate organic fraction extractant for microelements. Six top soils were extracted for Mn, Cu, Fe, and Zn in a boiling water bath with NaOCl alone (5.3%), NaOCl plus 0.005M DTPA (diethylenetriaminepentaacetic acid), or NaOCl with DTPA added during the last few minutes of extraction. Other variahles were time (15 or 30 min) and one or two extractions. The effects of each method on the Mn oxide and amorphous Fe oxide fractions were evaluated. A second extraction increased the amounts of metal ions extracted. Increasing extraction time solubilized additional Mn and Zn but the effect was less for Cu and Fe. NaOCl + DTPA extraction values for the metals were not different from those for NaOCl alone. Adding DTPA during the last few minutes of extraction greatly increased the amounts of extractable metals. When DTPA was added at the end, metal values for the Mn oxide and amorphous Fe oxide fractions were significantly less than for the other two treatments. Two 30‐min extractions with NaOCl alone are recommended. Since it appeared to extract microelements from the oxide fractions under these conditions, DTPA should not be added.
Genesis and Properties of Paleustalfs of North Central Texas: Morphological, Physical, and Chemical Properties
Authors: Stahnke C. R. , Wilding L. P. , Moore J. D. , Drees L. R.
Published: July 2010

The Windthorst and Chaney soils are characterized physically by relatively sandy surfaces, well‐developed argillic horizons that have a clay maximum in the upper Bt, and substrata that are dominated by sandstone. Chemically, they are characterized by a moderately acid to neutral reaction and an exchangeable cation suite dominated by Ca and Mg. A genetic relationship between these soils and the sandstone substrata is suggested by transect studies, morphological data, and particlesize data. However, particle‐size data also strongly indicate a substantial influence by parent materials other than sandstone. Field relationships, namely a marked lateral change in soil texture and other properties near the limestone‐sandstone contact, and evidence of downslope pedisediment transport of limestone residuum cast doubt on the importance of eolian additions as a primary pedogenic process responsible for observed textural differentiation. Though major eolian additions appear improbable, localized wind‐reworking of surface horizons of these soils has likely been significant. Shale and siltstone interstratified with sandstone have contributed to the clay content of some pedons, but interbedded argillaceous sediments are not prerequisite for the formation of these soils. However, gradual sedimentary grading from sandstone to finer‐textured strata during bedrock formation cannot be ruled out as possible clay sources for the argillic horizon. Microfabric analyses verify the concurrence between textural clay maxima and strongly developed argillic horizons. Between 9 and 15% of the cross‐sectional area of upper Bt horizons is comprised of moderately to strongly oriented illuvial void and grain ferriargillans. Abundance and the illuviated character of argillans decrease with depth to Cr horizons which have granular fabrics with thin, embedded, and free‐grain argillans inherited during sandstone formation.
Micromorphology of Polygenetic Soils in the Teays River Valley, Ohio
Authors: Thompson Michael L. , Smeck Neil E.
Published: July 2010

Soils in the preglacial Teays River Valley in Jackson County, Ohio, are polygenetic. Modern sola are developed in 50 to 60 cm of loess over loamy or silty colluvium which, in turn, overlies either weathered bedrock, old river alluvium, or thick lacustrine clay. Micromorphological observations of heterogeneous plasmic fabrics and embedded argillans and aggregates support the field identification of a paleosol developed in colluvium and buried hy loess. Abrupt changes in plasmic fahrics over short distances in thin section are interpreted to represent mixing of soil materials during colluviation. Compound argillans with varying degrees of orientation and disruption suggest that at least two periods of clay illuviation occurred. Discontinuous banding of plasma and silt particles suggests that the colluvium moved down valley walls during periods of solifiuction. We hypothesize that solifluction occurred about 18,000 RCYBP, when Wisconsinan ice had advanced to about 50 km northwest of the Teays Valley.
Changes in a Sandy Forest Soil Under Northern Hardwoods after 5 Years of Sewage Effluent Irrigation
Authors: Harris A. Ray , Urie Dean H.
Published: July 2010

Thinned and unthinned plots in a 50‐year‐old beech (Fagus sp.)‐maple (Acer sp.) stand in northwestern lower Michigan were irrigated with sewage lagoon effluent. After 5 years of effluent application at rates of 38 and 76 mm/week, litter weights were reduced, leaching was increased, and forest floor humus weights were increased. Irrigation also resulted in decreased organic matter in the mineral soil. Nitrogen and P were leached from the litter; Ca, Mg, and Na were retained in forest floor humus and mineral soil, greatly increasing the pH and base saturation. Nitrogen concentrations measured in leachate from the 120‐cm soil depth were consistently below 10 mg·L−1. Sodium was the predominant cation in the leachate. Irrigation over 5 years with wastewater effluent has had such minimal effects that higher irrigation rates might be considered without posing serious environmental risks.
Nitrogen Fertilizer Efficiency in Bermudagrass Production
Authors: Westerman R. L. , O'Hanlon R. J. , Fox G. L. , Minter D. L.
Published: July 2010

Efficient N applications are necessary to maximize bermudagrass (Cynodon dactylon L.) dry matter yield and N uptake in forage. Significant losses of NH3 from surface applications of urea and NH4‐N fertilizers by volatilization have been reported. Field experiments were conducted over a three‐year period under a wide range of climatic and soil conditions in Oklahoma to determine the efficiency of N applications for dry matter production and N uptake in bermudagrass forage. Four locations were selected in 1978 and one each in 1979 and 1980, representing four typical soil types for bermudagrass production with a pH range of 4.7 to 6.9. Anhydrous ammonia (AA) and ammonia passed through a Cold‐Flo adapter (ACF) were injected into bermudagrass sod and urea‐ammonium‐nitrate (UAN), urea, and (NH4)2SO4 (AS) were broadcast. Rates of N were 0, 112, 224, and 448 kg·ha−1 initially as well as 224, 336, and 448 kg·ha−1 in split applications. An additional experiment was established in 1980 to evaluate the effect of S on yield and N uptake. Rates of S were 0 and 64 kg · ha−1 and sources were elemental S, CaSO4 · 2H20, MgSO4, and AS. There were two harvests at each location in 1978, three in 1979, and two in 1980.

Yield and N uptake from AA and ACF applications were not significantly different, but generally were lower than with broadcast UAN, urea, and AS. Yield and N uptake generally were lower from urea than UAN and AS. Relative efficiency of N sources obtained from averaging across N response experiments were in the order of AS > UAN > urea > AA > ACF. Split application of N in 1978 and 1980 did not increase yield, but in 1979 an increase in yield was obtained with more even rainfall distribution during the growing season. Sulfur fertilization decreased N:S ratios in forage, but did not increase yield or N uptake or improve N efficiency. Potential losses of NH3 by volatilization from broadcast urea, UAN, and AS in these experiments were considered minimal.
Effects of Permanent Charge on the Electrical Double‐Layer Properties of Clays and Oxides
Authors: Kleijn W. B. , Oster J. D.
Published: July 2010

Two complimentary models which describe the surface chemistry of, respectively, clay minerals and oxides submersed in an aqueous solution are presented. Both models incorporate isomorphous‐substitution charge, specific adsorption of counter ions at the inner Helmholtz plane, and a diffuse double layer outside the outer Helmholtz plane. In addition, one of the models allows for adsorption of potential‐determining ions at the surface plane, which is located inward of the inner Helmholtz plane. General algorithms to solve surface chemistry models are given and methods to determine the associated empirical parameters are discussed. With the model which includes adsorption of potential‐determining ions, it is shown that isomorphous substitution may be of great importance to the adsorption properties of oxides. Based on published data for NaCl/Al2O3 and KCl/SiO2, computations are made which show that changes in the charge density of the potential‐determining ions adsorbed at the surface plane tend to be equal in magnitude but opposite in sign to changes in the isomorphous‐substitution charge density (σo). However, this cancellation is not perfect, and especially for KCl/SiO2 systems, the counter‐ion exchange capacity and its pH dependency and the zeta potential are strongly dependent on σo. The dependence on σo is particularly strong in the region where σo is small (−0.04 < σo < 0.02 C/m2). This implies that small amounts of isomorphous substitution may have a dramatic effect on the physico‐chemical properties of oxides. The ion‐adsorption behavior of montmorillonite cannot be explained with our generalized model for oxide surfaces. Thus, our calculations confirm the long‐standing view that the basal planes of clay minerals do not adsorb H+ and OH‐ as potential‐determining ions.
Determination of Total Arsenic in Soil by Differential Pulse Polarography
Authors: Elkhatib E. A. , Bennett O. L. , Wright R. J.
Published: July 2010

A technique was developed for the determination of total arsenic (As) in soil using differential pulse polarography. Soil samples were digested with a combination of HNO3 and H2SO4. Total As was determined in 1M HCl after reduction of As(V) to As(III) with hydrazine sulfate. Soil and fly ash standards were analyzed by this method and agreement within one standard deviation between replicates was obtained. Approximately 99% recovery of As was obtained from spiked soil samples.
Net Charge Characteristics of Dystrandept B and Theoretical Prediction
Authors: Wada Koji , Okamura Yutaka
Published: July 2010

The net charge characteristics of five Dystrandept B samples containing components with variable charge were described by combining the two empirical equations that relate the retention of NH4+ and Cl‐ with the pH (4 to 8) and NH4Cl concentration (0.005 to 0.1M) of the solution. There were two characteristic pH values; the point of zero charge (PZC) and the point of constant charge (PCC). The variation of PZC with NH4Cl concentration was appreciable, whereas that of PCC was very small or insignificant. The PZC was found in the range from pH 4.4 to 6.3, and the PCC pH was 4.9 to 6.0. The small net charge at PCC was positive for the soils containing allophane and imogolite and negative for the soil containing 2:1 layer silicates and gibbsite but not containing allophane and imogolite. The effects of the pH and NH4Cl concentration on the magnitude of the net charge are compatible with those calculated using the Stern theory of the electric double layer with an assumption that the thickness of the Stern layer (0.3 to 0.5 nm) decreases with increasing electrolyte concentration. The order of magnitude of the net charge measured is in agreement with that calculated.
Peroxy Radical Interactions with Soil Constituents
Authors: Pohlman A. A. , Mill T.
Published: July 2010

Interaction of peroxy (RO2·) radicals with soil constituents in dilute aqueous solutions and suspensions at 50°C was examined using p‐isopropylphenol (PIP) as a probe. Dissolved and suspended humic substances as well as suspended silicate surfaces were found to trap RO2· radicals. Competitive trapping of RO2· radicals occurs with 10 mg·L−1 of solid suspended humic acid polymers and by 1.0% silicate suspensions containing 3–74 mg·kg−1 of total organic C. Electron and H‐atom transfer between RO2· radicals and solid surfaces is attributed to the availability of electron‐donating or phenolic functional groups and not to total organic C content.
Improved Corrective Fertilizer Recommendations Based on a Two‐Step Alternative Usage of Soil Tests: III. The Bray‐1 Test on Soils with Concretions
Authors: Mostaghimi S. , McLean E.O.
Published: July 2010

Six soils from temperate and tropical regions and of wide range in P fixation tendency were treated with five rates of P. Portions of each P‐treated soil were equilibrated for 6‐weeks and tested for Bray‐1 P. Also, Bray‐1 P was computed for each soil and P treatment from P fixation factors determined by quicktest recovery of added P in Bray‐1 extract after a 2‐h equilibration. Actual amounts of fertilizer P required to reach sufficiency level of available P for near‐maximum yields (PSL = 20 µg·g−1 were obtained from the added P vs. Bray‐1 P relationship. Similarly, amounts of fertilizer P required for sufficiency levels in the soil were computed from constant 22.9% recovery for all soils, and from individual P fixation factors obtained by quicktest recovery of added P. The P‐treated soils were also cropped to corn (Zea Mays) in a growth chamber. Yields and P contents of tissue were measured. The computed fertilizer P values for PSL = 20 from quicktest recovery of added P after 2‐h equilibration were highly correlated with the actual amounts found by 6‐week equilibration (r2 = 0.831). Use of this second step, in which the quicktest‐computed values are regressed to the equivalent of actual (6‐week) values, make the average deviation from the actual values only 29 compared to 182% when computed on the basis of 22.9% recovery of P from all soils. When the Fe and Mn concretions in the Delicias soil (Oxisol) were crushed and the 2‐h equilibration extended to 24 h, the r2 value for computed vs. actual values was 0.983, and the average deviation of quicktest computed from the actual values for the six soils was only 15%. Quadratic regression showed that the Bray‐1 P accounted for 81% of the variation in the yields, while linear regression showed Bray‐1 P accounted for this same percent of the variation in P contents of the corn seedlings. When the soils were grouped into populations according to the factor for efficiency of recovery of available P, c1, correlation of the yield component data [log(A‐y)] with corresponding Bray‐1 soil available‐P component data (c̄1x in the Mitscherlich‐Bray equation gave r2 = 0.884.
Testing Chemical Criteria for Spodic Horizons on Podzolic Soils in Canada
Authors: McKeague J. A. , Wang C. , Coen G. M. , DeKimpe C. R. , Laverdiere M. R. , Evans L. J. , Kloosterman B. , Green A. J.
Published: July 2010

Application of chemical criteria of the spodic horizon to 220 Podzolic pedons from Canada excluded 157 of them from Spodosols. Failure of approximately 60% to meet the required ratio (0.2) of pyrophosphate‐extractable (Fe + Al) to clay was the principal factor. The requirement that at least one‐half of the dithionite‐citrate extractable (Fe + Al) be extractable by pyrophosphate was not met by approximately 40% of the Podzolic pedons. Modified chemical criteria for the spodic horizons are proposed.
Oven Drying as a Pretreatment for Surface‐Area Determinations of Soils and Clays
Authors: Ratner‐Zohar Yael , Banin A. , Chen Y.
Published: July 2010

Various procedures for drying soil and clay samples prior to surface area determination have been compared. The study was conducted on various soils—kaolinite, illite, and a number of minerals representing the smectite group. This research showed that 24 h of oven drying rather than P2O5 drying can be applied as a pretreatment for surface‐area determinations of soils and clays by the ethylene glycol monoethyl ether (EGME) method with the exception of illite and illitic soils. Surface‐area determinations following the two drying procedures were highly significantly correlated (at the 1% level) for smectites and soils, exhibiting coefficients of 0.996 and 0.986, respectively, between the oven‐ vs. P2O5 drying. Oven drying results in a 15% decrease in surface area of illite, suggesting that this procedure would not be recommended as a pretreatment for measurements on soils rich in illites. The oven drying procedure saves 4 to 5 d of the surface‐area determination procedure and is applicable to smectites and soils rich in montmorillonite and kaolinite.
Some Characteristics of Rhizobium meliloti Isolates from Alfalfa Fields in Oregon
Authors: Bottomley P. J. , Jenkins M. B.
Published: July 2010

Field populations of Rhizobium meliloti were sampled from root nodules of alfalfa (Medicago sativa L.) growing in 61 sites in five regions of Oregon. In four of the regions, 60 to 92% of the sites had no previous history of alfalfa. Most probable number (MPN) determinations of R. meliloti in the soils of these regions showed that 50 to 70% of the sites possessed < 104 R. meliloti/g of soil, and 17 to 50% had plants showing extremely poor nodulation. Neither preinoculation nor slurry/dusting inoculation practices had been completely satisfactory. In effectiveness studies, only 24 isolates out of 422 evaluated could be classed as superior N fixers. That is, they produced plants equal in weight to nitrate‐grown plants. Twenty‐eight to forty‐four percent of isolates within each region were inferior N fixers, and 40 to 58% of the sites in each region contained 50% or more inferior isolates. Only in 13% of sites were inferior isolates absent. The highest percentage of inferior isolates was found in the Willamette Valley, where most sites had (i) a long history of alfalfa, (ii) the largest soil populations of R. meliloti, and (iii) suboptimum fertility levels.
Mineralogy of the Major Soils of the Gezira Scheme (Sudan)
Authors: Adam A. I. , Anderson W. B. , Dixon J. B.
Published: July 2010

The major soil series comprising the Gezira scheme are Hosh, Suleimi, and Laota. These soils are calcareous, dark brown to grayish brown clays with low organic matter contents (< 1%). The mineralogical properties of these soils were studied by X‐ray diffraction (XRD), dissolution, and Ca/Mg and K/NH4 cation exchange capacities. Some complementary data were obtained using infrared (IR) spectroscopy. The results of the study reveal that these soils have similar sand, silt, and clay mineralogy. The sand fractions are composed of quartz, plagioclase, K feldspars, anatase, and amphiboles. The silt fractions contain, in addition to the above minerals, kaolinite, mica, and chlorite. The coarse clay is composed of chlorite, kaolinite, smectite, plagioclase and K‐feldspars, quartz, and mica. The fine clay is predominantly smectite (a mixture of montmorillonite and beidellite), kaolinite, and mica. Calcite is the dominant mineral in the gray hard nodules. The uniform physiographic position and similar mineralogy of these soils suggest that they have a common origin. The similarity in mineralogical composition to that of the recent sediments of the Blue Nile and its tributaries, supports the contention that the Gezira soils have inherited their mineralogical properties from the source area of the sediments in Ethiopia.
Rapid Estimation of Iron Oxides in Soils and Clays by Spectrophotometric Analysis
Authors: Fey M. V. , Dixon J. B.
Published: July 2010

A simple, rapid method is presented for the determination of Fe in soils and other ferruginous materials involving hot 6M HCl digestion followed by colorimetric analysis of the ferric chloride complex at 365 nm. Absorbance is linear up to Fe concentrations of at least 40 mg/L. An interference by oxalate in solution was found to be small enough to permit the analysis of iron oxide residues after acid ammonium oxalate treatment. No other significant interferences were found.
Sampling Volume Effects on Determining Salt in a Soil Profile
Authors: Hassan H. M. , Warrick A. W. , Amoozegar‐Fard A.
Published: July 2010

The effects of soil sampling volume for determining salt present were investigated in situ. Six 2.2‐m2 plots were hand sprinkled over a 5‐d period with a total of 10 cm of water containing 1000 mg/L of chloride as CaCl2. Soil samples were taken at three locations within each plot at 10‐cm increments to 100 cm and at 20‐cm increments to the 160‐cm depth. Two different samplers, 7.9‐ and 2.1‐cm diameter, were used. The salt concentration was measured on a 2:1 extract. The measurements for the larger samples were less variable than the smaller samples. The coefficient of variability (CV) for the total chloride recovered was 8 and 14% for the large and small samples, respectively. In order to compare favorably to the known amount added, the effective radius of the sampling tool was critical. The CV for the chloride concentration calculated in the soil water ranged from 5 to 54% and 12 to 199% for large and small samples by depth.
Potassium‐Calcium Exchange in a Multireactive Soil System: II. Thermodynamics
Authors: Jardine P. M. , Sparks D. L.
Published: July 2010

Thermodynamics of K exchange were investigated in Ca‐saturated samples from the Ap horizon of an Evesboro soil from Delaware. At 283 and 298 K the selectivity curves (lnkv vs. X̄K) showed preference for K at low values of NK (mole fraction of K in solution) and for Ca at higher values. This selectivity reversal may be attributed to exchange sites of varying reactivity for K and Ca ions and supports the hypothesis of the multireactive nature of the soil. Although K was selectively bound at low NK, the soil exhibited an overall Ca preference as noted by the positive standard free energy values (ΔG°). The standard enthalpy of exchange (ΔH°) was negative, which indicated very strong binding of K ions with some sites of the soil. This may be associated with the presence of vermiculitic clay minerals that predominated in the <2‐µm clay fraction. A thermodynamic investigation was also initiated on the various size fractions of the soil (i.e., sand, silt, and clay) and on soil that was treated with cetyltrimethylammonium bromide (CTAB) or NaOCl‐DCB. These treatments explained the differences in ionic selectivity observed in the Evesboro soil.
Net Aerial Primary Production and Dynamics of Soil Organic Matter Formation in a Tidal Marsh Ecosystem
Authors: Hsieh Y. P. , Weber O. J.
Published: July 2010

Relationships between net aerial primary production (NAPP) and soil organic matter formation in a tidal marsh environment were analyzed using a dynamic model. Four basic parameters were considered in the model: NAPP, disappearance rate of dead standing crop, and rates of plant decomposition in soil and air. The model was tested in a sawgrass (Cladium jamaicense) tidal marsh of north Florida. Net aerial primary production was estimated to be 2643 g m−2 y−1 using a paired‐plot method. The mean annual disappearance rate of dead standing crop was estimated to be 1.965 g g−1 y−1. The disappearance rate of sawgrass in soil was estimated to be 4.308 g g−1 y−1 for the labile portion and 0.105 g g−1 y−1 for the resistant portion. The sawgrass consists of 34% labile and 66% resistant portions. The soil organic matter due to NAPP was estimated to be 12.5 kg m−2. The actual soil organic matter under the marsh was found to be about 100 kg m−2. Most of the soil organic matter was preserved by constant submergence in water and, therefore, did not actively participate in the carbon cycle. Only about 20 kg m−2 of the soil organic matter that had an average thickness of 30 cm was considered to be actively participating in the carbon cycle. The dynamic model predicted 30 y is needed for soil organic matter to be stabilized, and < 2 years is needed for dead standing crop to be stabilized under the environment. Ninety‐eight percent of the soil organic matter was from the resistant pool of sawgrass. The mean fraction remaining (MFR) of the soil organic matter was 0.36. Two carbon cycles were defined in the marsh soil: the short one (mean retention time = 0.73 y) is probably important to the food and energy supply of the ecosystem; the long one (mean retention time = 10 y) comprises the major portion of the soil organic matter.
Mineralizable Soil Nitrogen: Amounts and Extractability Ratios
Authors: Juma N. G. , Paul E. A.
Published: July 2010

Studies were conducted on a 15N‐labeled Weirdale loam, a Dark Gray Chernozemic soil (Boralfic Boroll) to (i) determine the amounts of N released by several methods previously used to obtain an estimate of potentially mineralizable N, (ii) determine their 15N enrichment and extractability ratios, and (iii) compare the results from the above with the N mineralized during incubation and NH+4 released by the chloroform fumigation incubation technique. The NH+4‐N accumulated during 10 d in fumigated soils accounted for ∼1% of total N, was highly labeled, and had extractability ratios of 6.6 to 7.4. These ratios were similar to ones obtained for N mineralized during incubation of unfumigated soils. Ammonium‐N extracted with dilute acidic permanganate solution (0.01M KMnO4 in 0.1 or 0.5M H2SO4) accounted for 0.72 to 0.84% of total N and had extractability ratios ranging from 3.4 to 3.9. A stronger solution of acidic permanganate extracted more N that was less enriched. Dilute sulfuric acid extracted NH+4 and organic N that had extractability ratios of < 3. Ammonium‐N released by autoclaving the soil accounted for ∼1% of total N and had extractability ratios ranging from 0.6 to 0.9. Acid hydrolysis showed that 72% of total N was hydrolyzable, 32% was amino acid‐N and 20% was NH+4 released on hydrolysis. The extractability ratio for NH+4 released on hydrolysis was 1.7 and was significantly (P < 0.01) greater than extractability ratios of hydrolyzable N and amino acid‐N. The similarity and high extractability ratios of NH+4 released after fumigation and NO‐3‐N accumulating during aerobic incubation indicated that the fumigation extracted a biologically meaningful fraction. The biomass was responsible for only 15 to 25% of the net N mineralized during a 12‐week incubation. Results indicated that (i) extraction of a highly labeled N pool in soil can only partly explain the source of N being mineralized, (ii) N is mineralized from several pools, and (iii) there is a remote possibility that a single extractant can extract the variety of N compounds undergoing mineralization and immobilization in soil.
Nitrogen‐15 Balance and Residual Effects of Urea‐N in Wetland Rice Fields as Affected by Deep Placement Techniques
Authors: Cao Zhi‐hong , De Datta S.K. , Fillery I.R.P
Published: July 2010

The 15N balance at harvest, the residual effects of applied N fertilizer, and the distribution of N by depth in a wetland rice (Oryza sativa L.) soil (Alfisol) were determined in field experiments using 15N‐labeled urea. Nitrogen‐15 balance data show that with point, deep placement of urea supergranules (USG), only 4 to 5% of the applied N was unaccounted for after harvest of both the dry‐season and wet‐season crops. In contrast, when prilled urea was basally broadcast and incorporated and topdressed at panicle initiation (PI), 11 to 35% of the applied N was not recovered at harvest, indicating substantial loss of fertilizer N, especially when poor incorporation resulted in high floodwater mineral‐N levels. Uniform deep placement also resulted in high recovery of 15N (92–107%), confirming that the high total 15N recovery obtained with point deep‐placement of USG was largely a function of depth of placement. Band application of urea gave complete 15N recovery (102%) in the dry season and low recovery (61%) in the wet. Nitrogen‐15 balance data showed that 22 to 56% of the applied urea‐N still remained in the soil after the final harvest. The uptake by the wet season crop of the residual labeled soil N from the dry season experiment was about 5% of the initial applied N (87 kg N/ha) for all treatments. Placement method appeared to influence the actual recovery of residual soil 15N; the percentage recovery from the USG treatment was highest and that from the split urea treatment lowest. In neither the dry season nor the wet season was 15N enrichment significant in soil below 30 cm. Generally, the distribution of the residual 15N in soil reflected the placement pattern of urea.
Amino Sugar Distribution in Four Soils as Determined by High Resolution Gas Chromatography
Authors: Benzing‐Purdie Laure
Published: July 2010

High Performance Gas Chromatography (HPGC) was used for the accurate determination of glucosamine and galactosamine in soil hydrolysate fractions of different particle sizes, the water soluble and plant residue fractions of four cultivated soils: a clay and clay loam soil with grain cover, a sandy loam and loamy sand with corn (Zea mays L.) cover. Results showed in all instances, a parallel between organic C, N, and amino sugar content, with a definite enrichment in organic matter and amino sugars in the small particle‐size fractions in the sandy loam and loam sand soils. An accumulation of amino sugars was observed in the smaller particle‐size fraction of the clay loam acid soil.