bluuebunny/crossref_metadata_2025 huggingface dataset:
Aluminum Toxicity and Calcium Deficiency in Acid Subsoil Horizons of Two Coastal Plains Soil Series
Authors: Adams Fred , Hathcock P. J.
Published: July 2010

Inadequate root proliferation in acid subsoil horizons of the Coastal Plain of the southeastern United States limits yields of many crops. The recognized root‐limiting chemical factors in these soils are Al toxicity and Ca deficiency, but it is not known if these properties can be predicted from soil series descriptions. In an effort to delineate Al toxicity and Ca deficiency by horizon and by soil series, six representative profiles from each of two major soil series of Alabama's Coastal Plain were sampled by horizon to a depth of 1 m. Three profiles from each of two major soil series were obtained from cultivated fields; the other three were obtained from adjacent woodlands. Horizon samples were subdivided and treated with one of the following: (i) check, or no treatment, (ii) CaSO4, (iii) MgO, and (iv) Ca(OH)2. Growth rate of cotton (Gossypium hirsutum L.) taproots into each treated soil material was measured, and visual symptoms of Al toxicity and Ca deficiency on roots were noted. Six of seven Bt horizons in the Orangeburg series were Al toxic; four of 12 in the Dothan series were Al toxic. None of the five BE horizons were Al toxic. Seven Dothan horizons and four Orangeburg horizons were Ca deficient. No Ca‐deficient horizon occurred in cultivated fields and no Al‐toxic horizon occurred in woodlands. Aluminum toxicity occurred in some Bt horizons (but not all) of cultivated fields when soil‐solution Al was only 0.4µM, but not in BE horizons of woodlands where solution Al ranged up to 11.5µM by the 8‐hydroxyquinoline method. Neither was Al saturation a satisfactory predictor of Al toxicity. Nondeficient Ca levels (both soil solution and exchangeable) were lower in cultivated fields than in woodlands. There was no apparent difference between soil series relative to Ca deficiency and Al toxicity, making it seem unlikely that soil classification will be helpful in predicting Ca deficiency and Al toxicity in subsoil horizons.
Detecting Soils under Cultural Vegetation Using Digital Landsat Thematic Mapper Data
Authors: Thompson D. R. , Henderson K. E.
Published: July 2010

Aircraft thematic mapper simulator (TMS) and Landsat‐4 Thematic Mapper (TM) data from the same site were examined for their relative accuracy in separating soils of an intensely cultivated agricultural area. Data from five different dates throughout the 1982 growing season of corn (Zea mays L.) and soybeans [Glycine max (L.) Merr.] were used in this study. Soils under corn canopy were separated at the soil mapping unit level with an accuracy of 55.5% and soils under soybeans at an accuracy of 46% on the 23 June date. As these soils are similar in their physical and taxonomic classifications, frequent errors could be expected at the mapping unit level. As the vegetative cover increased, the errors also increased, which could be expected. At the subgroup level, however, and at the great group level, the classification accuracy of soil groups increased. The great group level was separable with greater than 60% accuracy throughout the growing season. The TMS data on 23 June had the highest accuracy (92.9 for corn and 75.6 for soybeans). The 3 September TM data, even with > 90% ground cover, separated the great group level with 72.5% accuracy for corn and 68% accuracy for soybeans. The results of this study indicate that the improved spectral and spatial resolution of TM offers the potential to separate important soil properties even in a region with similar soils and under a dense vegetation canopy.
The Influence of Aluminum on Iron Oxides: XI. Aluminum‐Substituted Maghemite in Soils and Its Formation
Authors: Schwertmann U. , Fechter H.
Published: July 2010

Maghemites (γ‐Fe2O3) from highly weathered soils had unit cell parameters significantly lower than pure maghemites. This was due to Al for Fe substitution in the cubic structure. Al‐substituted maghemites were synthesized by heating soil and synthetic Al‐substituted goethites with sucrose and synthetic Al‐substituted magnetites. Formation of Al‐substituted maghemites in soils by fire is, therefore, postulated.
Evaluation of Closed‐Form Analytical Models to Calculate Conductivity in a Fine Sand
Authors: Stephens Daniel B. , Rehfeldt Kenneth R.
Published: July 2010

The soil‐water characteristic curve, θ—ψ, was determined for an undisturbed core of fine sand over a range of negative pressure heads observed in the field, 0 to 150 cm, below about the 30 cm depth. These data were used to predict relative hydraulic conductivity in a computer code of closed‐form analytical solutions developed by van Genuchten for the theoretical models of Burdine and Mualem. The equations to predict conductivity are based upon two parameters fit to observed θ—ψ data by a non‐linear least squares procedure. The two parameters are influenced by the choice of residual water content, θr, and unsaturated water content, θs. If θr is unknown, it is estimated in the program from observed data. A sensitivity analysis was performed to evaluate the reliability of the models. For this soil, calculated conductivities appear to be sensitive to θr. If θ—ψ data are available over only a limited range, or if θs is too large, model‐predicted θr‐values may be near zero, whereas θ at large ψ may actually be about 0.06 to 0.08 cm3/cm3. Predicted conductivities may differ by more than one order of magnitude at about ψ = 150 cm, depending on the choice of θr.
Measurement of Soil Water Content using Time‐domain Reflectrometry (TDR): A Field Evaluation
Authors: Topp G. C. , Davis J. L.
Published: July 2010

For measurement of water content using TDR, parallel wire transmission lines varying in length from 0.125 to 1 m were installed vertically at planting time at three sites in a corn field. At one of the sites horizontal lines and additional vertical transmission lines with electrical impedance discontinuities were installed for comparison. Measurements of water content using a portable TDR cable tester were made periodically during the growing season. Comparisons of water contents by TDR with those from gravimetric samples showed that generally both were the same values. Standard deviations of differences between TDR and gravimetric values were ± 0.02 m3m−3 when measured locations were the same but increased to ± 0.06 m3m−3 when measured locations were different. Repeated measurements at the same location were highly correlated, one with another, over the season. Analysis of variance showed that all transmission line types were yielding equivalent values and that the horizontal transmission lines gave the minimum standard error of the mean. Data from transmission lines with impedance discontinuities gave water content profiles from a single measurement but the analyses of the TDR data curves were more complex than for the lines without impedance discontinuities. The variety of transmission line configurations for use in TDR measurement allows considerable flexibility of choice in relation to one's application.
Gas Displacement and Aggregate Stability of Soils
Authors: Kemper W. D. , Rosenau Russell , Nelson Sheldon
Published: July 2010

When surface soils are dry, O2 and N2 are adsorbed on the external mineral surfaces. In the process of wetting the soil, water molecules displace the adsorbed O2 and N2 molecules to the gas phase where they can be measured, as was done in this study. These gases, released from the adsorbed phase, join entrapped air in the gaseous phase as the primary factor disintegrating aggregates when soils are wet quickly. Adsorption of N2 and O2 occurs on surface soils during hot dry afternoons as the water molecules leave the surface. During cool nights, relative humidities commonly rise above 50%, allowing more strongly adsorbed H2O molecules to displace adsorbed O2 and N2. Release of this adsorbed N2 and O2 causes aggregates wetted by immersion during hot afternoons to be less stable than aggregates of the same soil wetted in the morning.
Effect of Temperature‐dependent Hydraulic Properties on Soil Water Movement
Authors: Hopmans J. W. , Dane J. H.
Published: July 2010

Thermal effects on the soil water regime are often ignored. In addition to the effects of temperature on the driving forces for flow, there are also direct thermal effects on the soil's hydraulic properties. Accounting for this temperature dependency of the soil's hydraulic properties, the pressure head form of the general flow equation of water was solved by the predictor‐corrector method for different temperature regimes and for a variety of initial and boundary conditions. Corrections of soil hydraulic properties due to temperature changes were either based on experimental data extracted from the literature or on theoretical considerations. Temperature effects were found to be much more pronounced for a pressure head than for a flux boundary condition at the soil surface. For temperature varying with both time and depth, the effect seemed to be minimal if the hydraulic properties were determined at the mean temperature of the profile. The latter suggests that soil hydraulic properties determined in the laboratory, but to be used for field conditions, should probably be determined at a temperature that approaches the mean field soil temperature. The simulations also showed that temperature effects are more pronounced as the temperature coefficient of soil‐water‐pressure‐head increases, but that the kind of effect depends on whether the existing temperature is above or below the reference temperature (temperature at which the hydraulic properties were determined).
Fertilizing Agricultural Land with Rainbow Trout Manure for Growing Silage Corn
Authors: Smith J. H.
Published: July 2010

Field plots on a Portneuf silt loam (mesic, Durixerollic Calciothids) were fertilized with fish manure at 0, 200, 500, or 800 kg N/ha or NH4NO3 at 0, 100, 200, and 300 kg N/ha for one, two, or three years and planted to corn (Zea mays L.) for four consecutive years. Corn silage yields up to 24 Mg/ha (dry weight) were obtained the first season in 1979 with no significant differences because of the high residual fertility. Highly significant yield increases were obtained the second, third, and fourth season from manure or NH4NO3. The yields were somewhat lower than those obtained the first season. In four years of cropping to corn with manure applied for the first three crops, N recovery for the manure treatments was 18, 28, and 24% of applied manure N for the 200, 500, and 800 kg N/ha applications for three years. In comparison treatments using NH4NO3, N recovery was 90, 59, and 57% for the 100, 200, and 300 kg N/ha treatments. The manure applications at 500 kg N/ha provlded enough N for high corn silage yields and were about equal to the yields obtained with 200 kg N/ha as NH4NO3. Residual N fertility from the manure was greater than from NH4NO3.
Effect of Preplant Wheel Traffic on Soil Compaction, Water Use, and Growth of Spring Wheat
Authors: Voorhees W. B. , Evans S. D. , Warnes D. D.
Published: July 2010

The effects of wheel traffic on small grain emergence and early growth is commonly observed in production fields. However, the plant response is not consistent, but appears dependent on soil and climatic conditions. The objective of this study was to measure the effects of preplanting wheel traffic on soil compaction and ‘Era’ spring wheat (Triticum aestivum L.) growth in field plots in West Central Minnesota under a range of growing season conditions. The 1975 and 1977 growing season were slightly wetter than normal while the 1976 growing season was significantly drier. Treatment comparisons were wheat planted in soil compacted by wheel traffic during spring field operations and wheat planted in soil that had not been wheel trafficked. Normal field‐sized equipment (tractor weight ranged from 4000 to 7000 kg) was used to perform spring fertilizer application, spring tillage, and seeding. The controlled wheel traffic concept was used. In 1975, wheat emergence in the wheel‐tracked soil was delayed by about 10 d because of poor seed‐soil contact, and grain yield was 27% lower than in the nontracked soil. Shortly after planting in 1976, the nontracked soil lost excessive amounts of water by evaporation from the loose 0‐ to 0.15‐m layer. As a result, wheat growth in the wheel‐tracked soil was better than in the nontracked soil, and yield was increased by 53%. In both 1975 and 1976, there was slightly more water used from the wheel‐tracked treatment than from the nontracked treatment, resulting in differences in water use efficiency. Effects of wheel traffic on wheat growth and yield were closely related to growing season precipitation and illustrate the need to consider probable climatic conditions when developing management systems for controlling field vehicular wheel traffic.
Ammonium Nitrogen Movement in a Coarse‐Textured Soil Amended with Zeolite
Authors: MacKown C. T. , Tucker T. C.
Published: July 2010

Leaching of NH+4 from coarse‐textured soils treated with nitrification inhibitors is affected by the soil cation exchange capacity (CEC), the presence of other ions, and the percolation rate. Natural zeolites have unique chemical and physical properties that could enhance the retention of monovalent cations in coarse‐textured soils.

Column experiments to evaluate NH+4 movement in Rositas loamy sand (Typic Torripsamment) amended with erionite (E) or clinoptilolite (K) natural zeolite at rates of 0, 12.5, 25.0 and 50.0 g zeolite kg−1 soil were conducted. Water saturated soil‐zeolite mixtures (1.0 kg) received 200 mg NH+4‐N and were leached with 3.0 liters (150 cm) of deionized water containing a nitrification inhibitor [2‐chloro‐6‐(trichloromethyl) pyridine]. Total NH+4‐N leached ranged from 168.4 mg N for the unamended soil (CEC = 29 cmol(+) kg−1) to 11.6 mg N for the 50.0 g E kg soil (CEC = 102 cmol(+) kg−1). Total effluent NH+4‐N at a given amendment rate was less from zeolite E(CEC = 1570 cmol(+) kg−1) than zeolite K (CEC = 1140 cmol(+) kg−1). The distribution of NH+4 recovered in 5‐cm increments was dependent on the CEC of the soil‐zeolite mixture. As the CEC increased, the depth of maximum accumulation decreased. These results indicate that zeolites effectively enhanced the retention of NH+4 subject to leaching and zeolite application per unit soil volume may be maximized by restricting the depth of incorporation.
Nitrification Inhibition by Nitrapyrin and Volatile Sulfur Compounds
Authors: Maddux L. D. , Kissel D. E. , Ball J. D. , Raney R. J.
Published: July 2010

Nitrification inhibitors can slow the rate of nitrification in soils and reduce nitrogen losses under some soil‐climatic conditions. Carbon disulfide (CS2) and compounds which produce CS2 have slowed nitrification in laboratory studies, but these compounds have not been tested extensively in the field. Therefore, field studies were conducted on irrigated corn (Zea mays L.) in 1978 and 1979 to evaluate inhibition of nitrification by CS2 at 5.6, 11 and 22 kg ha−1, sodium trithiocarbonate (STC) at 11 and 22 kg ha−1, ammonium dithiocarbamate (ADTC) at 11 and 22 kg ha−1, and potassium ethyl xanthate (KEtX) at 5.6 and 11 kg ha−1 as compared to nitrapyrin (2‐chloro‐6‐(trichloromethyl)‐pyridine) at 5.6 kg ha−1. Anhydrous ammonia was knifed 15 to 20 cm deep on 60 cm spacings at rates of 84, 168, and 252 kg N ha−1. All materials were evaluated on a Eudora fine sandy loam (Fluventic Hapludoll, coarse, silty mesic) in 1979 and CS2 and STC were evaluated on the same soil in 1978 and on two additional soils in 1979: a Pratt loamy fine sand (Psammentic Haplustalf, sandy, mixed, mesic) and a Crete silty loam (Pachic Argiustoll, fine, montmorillonitic, mesic). The performance of STC and CS2 in 1978 and 1979 indicated that these materials were not effective in inhibiting nitrification under the conditions that existed at the locations where they were applied. ADTC and KEtX were not effective inhibitors of nitrification, although they were only tested at one location in 1979. Nitrapyrin was effective in inhibiting nitrification in all studies. However, it resulted in an increase in corn yield only once—the fall N application on the Pratt loamy fine sand. The lack of yield response was attributed to the absence of conditions conducive for losses of nitrate nitrogen.
Distribution of Palygorskite in Sediments and Soils of Eastern Saudi Arabia
Authors: Shadfan Harbi , Mashhady A.S.
Published: July 2010

Rock samples representing different soil parent materials from the Jurassic, Cretaceous and Tertiary periods in eastern Saudi Arabia were investigated for their mineralogical and chemical properties. Samples from five soil profiles found on these rocks also were studied. Palygorskite was found to be the dominant mineral in the clay fraction of the Tertiary and upper Cretaceous sediments. Some shales of Tertiary origin contained mainly palygorskite with minor amounts of gypsum and soluble salts. Palygorskite was not found in any sediments of the early lower Cretaceous and Jurassic periods, and kaolinite was the dominant mineral in the clay fraction of those sediments. Soils associated with Jurassic limestone near the Riyadh area also showed a predominance of kaolinite in their clay fractions. However, the clay fractions of the soils found on Tertiary sediments in the eastern part of the country were dominated by palygorskite. The presence of palygorskite in the soils paralleled its presence in the parent materials or the rocks exposed in the area. Eolian transport of palygorskite was found to be a factor for the occurrence of palygorskite in the soils. Thus, the major portion of the soil palygorskite probably originated from the Tertiary sediments in eastern Saudi Arabia.
Nature and Behavior of Montmorillonite in an Acid Inland Marine Shale from East Central Saskatchewan
Authors: Curtin D. , Mermut A. R.
Published: July 2010

The mineralogy and chemistry of an acid clayey Cretaceous marine shale outcropping near Arborfield in east central Saskatchewan were studied. pH values as low as 3.6 and levels of exchangeable Aluminum of up to 28 cmol(+).kg−1 were recorded in this material. Clay separates of the shale were monomineralic, consisting of highly crystalline smectite (montmorillonite) with an average composition: M+0.71 (Si7.74Al0.26) (Al3.44Fe3+ 0.12Mg0.45)O20(OH)4 Ion activity product values, calculated from saturation extract composition data, indicated that the montmorillonite is stable despite the intense acidity of the shale. The high pH values (up to 8.5) which were observed in the upper soil horizons overlying the shale are due to the incorporation, by glacial action, of calcareous till into the shale. This till was apparently the source of the mica, kaolinite, and quartz present along with the montmorillonite in clays isolated from the upper horizons. The implications of the findings to the genesis and chemical characteristics of Saskatchewan soils are discussed.
Surface Soil Water Content Measurement Using Pulsed Nuclear Magnetic Resonance Techniques
Authors: Paetzold R. F. , Matzkanin G. A. , De Los Santos A.
Published: July 2010

A tractor‐mounted pulsed nuclear magnetic resonance (NMR) moisture measurement instrument has been developed and fabricated for use in collecting ground truth data for calibrating and evaluating remotely sensed determinations. The measurement approach is based upon NMR which depends on the interaction between hydrogen nuclear magnetic moments and a magnetic field. The sensor unit, consisting of an electromagnet, detection coil, and tuning capacitor, is towed behind the tractor and provides continuous readout of the volumetric soil water content at selected depths to 63 mm. Preliminary laboratory measurements with this instrument on two soils, a clay and a loamy fine sand, correlate linearly with volumetric soil water content. Discrimination of water NMR signals from signals from other hydrogen‐bearing material is based on nuclear relaxation times, which reflect the molecular environment and structural bonding characteristics of the water molecules in the soil.
Fluoride Sorption and Desorption in Soils
Authors: Peek Daniel C. , Volk V. V.
Published: July 2010

Fluoride sorption and desorption reactions in 10 soils were investigated. Fluoride sorption kinetic data were obtained by equilibrating 1.0 mmol/L NaF solutions with four soils for periods from 1 h to 77 d. Fluoride sorption reactions with respect to soil properties were examined by equilibrating 0.0 to 2.5 mmol/L NaF solutions with 10 soils for 24 h. Fluoride sorption was rapid in all soils, with 90% of the sorption occurring within 24 h. Increasing sorption equilibration time decreased the amount of F that could be desorbed from the soil in 24 h. Fluoride sorption conformed to the Langmuir sorption isotherm for all soils over limited concentration ranges. The Freundlich sorption isotherm was applicable over the entire initial F concentration range (0.0–2.5 mmol/L) for all soils. Simple and multiple regression techniques allowed various F sorption parameters to be predicted from selected soil properties. Oxalate‐extractable Fe and Al, dithionite‐extractable Al and soil pH correlated most highly with both Langmuir b and Freundlich K values in a simple regression model. A multiple regression equation including oxalate‐extractable Al, clay, and oxalate‐extractable Fe predicted 90% of the variation in Langmuir b values. Fluoride desorption also conformed to the Freundlich isotherm for all soils. Fluoride desorption was hysteretic in 7 of 10 soils, but hysteresis could not be explained by differences in measured soil properties.
Direct Measurement of Oxygen Profiles and Denitrification Rates in Soil Aggregates
Authors: Sexstone Alan J. , Revsbech Niels Peter , Parkin Timothy B. , Tiedje James M.
Published: July 2010

An oxygen microelectrode was modified to measure O2 concentrations in wet aggregates of a silt loam soil. The microelectrode tip had an O2‐permeable membrane opening 3 µm in diameter, and O2 measurements could be made in as little as 0.1‐mm increments to a depth of 12 mm. When aggregates were incubated in air, steep O2 gradients usually occurred over very small distances from the aggregate surface. The smallest aggregate exhibiting an anaerobic center had a radius of 4 mm, although small aggregates (radius ≤ 6 mm) were generally oxic. Larger aggregates (radius ≥ 10 mm) often had measureable anaerobic centers, with the exception of those from a native prairie soil which exhibited irregular O2 profiles and had aerobic centers, apparently due to O2 intrusion caused by old root channels. Oxygen profiles obtained in 45 degree increments around an aggregate circumference were used to construct contour maps of O2 concentrations within the aggregate. Oxygen gradients were somewhat asymmetric, suggesting nonuniformly distributed sites of O2 consumption. An average intra‐aggregate O2 diffusion coefficient of 8.5 × 10−6 cm2 · s−1 was measured for water‐saturated aggregates. The radii of anaerobic centers within several aggregates, measured directly with the electrode, correlated with those calculated from a model of radial diffusion using measured respiration rates and the intra‐aggregate O2 diffusion coefficient. Anaerobic centers were present in all aggregates that denitrified, but not all aggregates with anaerobic zones denitrified. The denitrification rate did not correlate with the size of the anaerobic zone, indicating that factors other than anaerobic volume contributed to the observed rates.
Manganese Nutrition of Flax as Affected by FeEDDHA and Soil Air Drying
Authors: Moraghan J. T.
Published: July 2010

Flax (Linum usitatissimum L.) accumulates large quantities of Mn, the uptake of which is reduced by a soil application of FeEDDHA, and develops Mn toxicity symptoms when grown on certain air‐dried, calcareous soils. Since soil Mn solubility is known to be enhanced by air drying, the influence of soil air drying on the abnormality was studied. Soil from the 0‐to 15‐cm depth of a Glyndon loam, a Calciaquoll, was collected from the field. After mixing for uniformity, half of the soil was air dried for 48 h while the other half was stored at 5°C (for 7 d) until required. The DTPA‐extractable Mn levels at planting in the air‐dried and non‐air‐dried soils were 4.2 and 1.9 µg g−1, respectively. Iron treatments of 0 and 2 µg FeEDDHA‐Fe g−1 were imposed on each soil condition. Flax grown on both soils without FeEDDHA developed symptoms of Mn toxicity, but the abnormality was more severe in plants grown on the air‐dried soil. Older leaves of flax contained 1758 and 1014 µg Mn g−1, respectively, when grown on the air‐dried and non‐air‐dried soils; FeEDDHA application reduced the above levels to 68 and 42 µg g−1, respectively, and eliminated all Mn toxicity symptoms. However, younger leaves became severely chlorotic when flax was grown on the FeEDDHA‐treated, non‐air‐dried soil. This FeEDDHA‐induced chlorosis was eliminated by foliar applications of MnSO4, so it was concluded that FeEDDHA had induced a Mn deficiency in flax.
Soil Test Phosphorus as a Regionalized Variable in Leveled Land
Authors: Knighton R. E. , James D. W.
Published: July 2010

Changes in spatial variability of soil test phosphorus (STP) after land leveling was studied using regionalized variable theory. Measurements were made on a regular grid and more intensive samples were taken between randomly selected grid nodes. Semivariograms showed anisotrophy and drift in the spatial structure of the data. The range of spatial structure was 25 m after leveling. Kriging was used to map STP and its associated error. Kriging was a better estimator than a fifth order bivariate polynomial. Soil test phosphorus was lognormally distributed and there were no significant differences between sample means before and after leveling. There was no significant correlation between depth of cut, fill and STP.
Mineralogical Variability within Clayey Soil Control Sections and Family Mineralogy Placement
Authors: Karathanasis A. D.
Published: July 2010

Mineralogical characterizations of 27 Alfisols and Ultisols indicated considerable variability among horizons comprising the control section. Coefficients of variation (CV) for dominant soil minerals critical for family mineralogy placement ranged from 5 to 173% within the same control section. Mineralogical variability within control sections caused 18 of the 27 pedons studied to be placed in incorrect mineralogy classes when mineralogical characterization data from the upper horizon of the control section were used. Using only upper control section mineralogy data, a policy favored by several characterization laboratories for time conservation, 11 pedons were misclassified as mixed instead of montmorillonitic, two mixed vs. illitic, two illitic vs. mixed, two montmorillonitic vs. illitic and one mixed vs. kaolinitic. A composite soil sampling technique utilizing preweighted subsamples from all control section horizons, constituting the upper 50 cm of the argillic according to their thickness, appears to satisfactorily predict the proper family mineralogy classification of soils lacking contrasting layers without increasing characterization time.
Preparation, X‐Ray Diffraction Pattern, and Solubility Product of Manganese(III) Phosphate Hydrate
Authors: Boyle F. W. , Lindsay W. L.
Published: July 2010

No characterization of MnPO4·1.5H2O (manganese [III] phosphate hydrate), other than x‐ray diffraction patterns, has been reported even though this compound has been recognized as a reaction product of manganese‐ and phosphorus‐containing solutions. Evaluation of the chemical and physical properties of MnPO4·1.5H2O is necessary prior to the study of this solid as a possible reaction product in soils. This mineral was prepared by reacting H3PO4 (orthophosphoric acid) with each of the following: MnCO3(c) (manganese [II] carbonate), MnOOH(c) (manganese [III] hydroxyoxide), and MnO(c) (manganese[II] monoxide). The reaction pathways were found to involve O2(g) as the electron acceptor. An intermediate compound, MnOOH(c), was isolated during the reaction by filtering the suspension following the cessation of CO2(g) evolution. X‐ray diffraction patterns were obtained and were matched with previously reported patterns. The refractive index was found to be approximately 1.73. The density was measured pycnometrically and was determined as being 2.5703 ± 0.0014 Mg m−3. The equilibrium constant (K°) for the following reaction: MnPO4·1.5H2O(c) = Mn2+ + PO3−4 + 1.5H2O was found to be 10−34.82 with σ = 0.46.
Oxidation of Iron in Biotite by Different Oxidizing Solutions at Room Temperature
Authors: Amonette J. , Ismail F. T. , Scott A. D.
Published: July 2010

Biotite samples (10–20 µm lepidomelane) were mixed with solutions that contained various oxidants (O2, NaOCl, H2O2, or Br2) and salts (NaCl, KCl, NaCl‐NaBPh4, or none) to compare the effectiveness with which these solutions oxidize structural Fe2+ at 25°C when customary procedures and mica samples at different stages of expansion are used. In general, the treatments that minimized interlayer K exchange did not oxidize detectable amounts of Fe2+, whereas those causing mica expansion oxidized equivalent fractions of the Fe2+ if they were given enough time. The rates of Fe2+ oxidation by the O2 and NaOCl‐O2 solutions were very slow in even the expanded mica and were similar enough to suggest the OCl‐ ions did not contribute to the process under these conditions. The Br2 and H2O2 treatments, on the other hand, oxidized 97 and 85% of the structural Fe2+ in a fully expanded mica, respectively, in a 24‐h period. The relative effects of Br2 and H2O2 solutions probably reflect differences in the oxidants themselves but are confounded by the low pH of the Br2 solution, NaBPh4 interactions and H2O2 decomposition. Indeed, all the results make it clear that more distinction needs to be made between the role of the oxidants and the side efects of the solutions and procedures that are used in oxidation experiments.
Spatial and Spectral Relationships of Soil Properties and Microtopography: I. Density and Thickness of A Horizon
Authors: Kachanoski R. G. , Rolston D. E. , de Jong E.
Published: July 2010

The effects of microtopography and an intertill stratigraphic sandgravel layer on the spatial variability of A horizon thickness, density, and mass are examined using standard, spatial, and spectral statistical methods. Soil cores (76 mm diam) were taken every 1 m in a 46 m long transect, in a native soil which is a mixture of Typic Haploborolls and Typic Argiborolls. The parent material is glacial till divided into two formations. The uppermost till is 1 to 2 m thick and is underlain by an intertill seed‐gravel layer of variable thickness. Microtopography parameters were estimated by fitting a least squares quadratic surface to elevation measurements around each soil core. Spectral estimates (coherency, cospectrum, phase spectrum) are calculated using smoothed Fourier methods. Standard correlation indicated a significant relationship between surface curvature in the direction of maximum surface gradient and A horizon thickness and mass; however, only 14% of the variability was explained. Thickness and mass of the A horizon had significant autocorrelation and spectral peaks indicating spatial cycling. The power spectra of A horizon thickness and mass were very similar to that of surface curvature. Coherency and cospectrums indicated that relationships between variables are complicated by phase shifts and opposite correlations in different frequency ranges. This was attributed to lateral water movement in surface depressions and the presence of both open and closed depressions. A horizon properties were not significantly related to the depth to the intertill sand‐gravel layer.
Spatial and Spectral Relationships of Soil Properties and Microtopography: II. Density and Thickness of B Horizon
Authors: Kachanoski R. G. , De Jong E. , Rolston D. E.
Published: July 2010

The effects of microtopography (<50 m) and an intertill stratigraphic sand‐gravel layer on the spatial variability of B horizon thickness, density, and mass are examined using standard, spatial, and spectral statistical methods. The relationships between A and B horizon thickness, density, and mass are also examined. Elevation and maximum surface gradient were significantly correlated to B horizon density. Microtopography parameters were not correlated to B horizon thickness or mass. The B horizon thickness and mass were significantly correlated to the depth to the intertill sand‐gravel layer. Significant autocorrelation was present in the density of the B horizon but not the A horizon. B horizon thickness and mass cycled significantly but at different frequencies than the A horizon. Spatial variability of the B horizon soil properties was related to the depth of the intertill sand‐gravel layer while the variability of the A horizon was related in large part to microtopography, especially curvature. Coherency and cospectral analysis indicated the B horizon mass had some relationship to surface curvature, but opposite correlation existed over different frequency ranges resulting in a non‐significant overall correlation. Average thickness, density, and mass of the solum did not have similar significant cycling or autocorrelation as was present in the individual horizons.
Temporal Stability of Spatially Measured Soil Water Probability Density Function
Authors: Vachaud G. , Passerat De Silans A. , Balabanis P. , Vauclin M.
Published: July 2010

Soil water data collected from three different fields are analyzed by two techniques (temporal analysis of the differences between individual and spatial average values; and Spearman's rank correlation) to search if time‐invariant characteristic statistical properties of the probability density functions can be assigned to individual locations. A grass field was equipped with 17 neutron access tubes and surveyed 24 times during a 2 1/2 yr‐period. In another field planted with olive trees, nine neutron access tubes were installed and quarterly measurements were performed during two consecutive years. The latter field cropped in wheat was gravimetrically sampled on a regular spatial pattern five different times and was routinely surveyed during a 1‐yr period at four selected locations by using a neutron moisture meter. All data show the existence of a very significant time‐stability of particular individual locations characterized by the same parameter in the statistical distribution of the observations taken over the field. It is shown that some locations conserve the property to represent the mean and extreme values of the field water content at any time along the year. This stability seems to be explained to a large extent by relationships between soil texture and water content.
Physical and Mineralogical Data to Determine Soil Hydraulic Properties
Authors: Puckett W. E. , Dane J. H. , Hajek B. F.
Published: July 2010

A study was conducted to determine relationships among physical, mineralogical, and soil hydraulic properties of Ultisols developed in unconsolidated sediments of the Lower Coastal Plain. Soil water retention curves, saturated hydraulic conductivity, bulk density, quantitative mineralogy, surface area, and particle size distribution were determined by horizon for seven pedons and relationships among them were analyzed by regression analysis procedures. Fine sand, sand and clay percentages were highly correlated with saturated hydraulic conductivity, surface area and volumetric water contents at specific pressure heads. Correlation coefficients > 0.95 were obtained for regression equations estimating soil water retention curves from particle size data. These relationships can be useful for quick characterization of soil hydraulic properties from particle size distribution data. No significant correlations were found between soil hydraulic and mineralogical properties of the clay fraction.
Chemical Modeling of Anion Competition on Goethite Using the Constant Capacitance Model
Authors: Goldberg Sabine
Published: July 2010

The constant capacitance model was used to describe phosphate, selenite and silicate adsorption on goethite (α‐FeOOH) in single anion systems. The model assumes a ligand exchange mechanism and considers the charge on both adsorbate and adsorbent. It is therefore appropriate for describing the adsorption behavior of these specifically adsorbed anions. The computer program FITEQL, a program that fits equilibrium constants to experimental data using an optimization technique, was used to obtain optimal values for the anion surface complexation constants on goethite. The model represented adsorption of these anions well over the entire pH range studied (3–12). The main advantage of the model is its ability to represent changes in anion adsorption occurring with changes in pH. Extension of the model to describing anion competition in mixed systems using the anion surface complexation constants from single anion systems was qualitatively successful. In mixed anion systems the model predictions reproduced the shape of the adsorption isotherms well over the pH range 3 to 12. However, phosphate adsorption was overestimated while adsorption of the competing anion was underestimated.
The Error Taxadjunct and Its Application in Soil Taxonomic Assignment
Authors: Hewitt A. E. , Van Wambeke A.
Published: July 2010

Precisely defined class limits cause taxonomic “splintering” of similar soils. This study follows up the suggestion in chapter 19 of Soil Taxonomy (USDA Soil Survey Staff, 1975) that knowledge of the confidence limits of measurement can allow “reasonable interpretations” which would prevent unwarranted splintering. A region of error adjacent to established taxa is identified, in which pedons, as representations of polypedons, are assigned to incorrect taxa because of errors in measurement of differentiating characteristics. This region is used to define the “error taxadjunct” which provides a means of softening precision of class limits. The size of the region of error is determined by the minimum acceptable probability of incorrectly assigning a pedon, as the representative of a polypedon, to a new taxon. Application of the error taxadjunct reduces taxonomic splintering. For this purpose the measurement errors of differentiating characteristics must be known, and the means of obtaining such data are reviewed. Examples show how the error taxadjunct can be used.
Application of a Statistical Soil‐Landscape Model to an Order III Wildland Soil Survey
Authors: Shovic H. F. , Montagne C.
Published: July 2010

Data organization, analysis, and documentation have long been a concern in the soil survey process. Existing computer aided systems are often either not widely available, not “user friendly,” or not very applicable to field mapping situations. These concerns are addressed using a simulation approach. A statistical model of the landscape and soils in the survey area is described. The data base used in the soil ‐landscape model consists of discrete sample points that are randomly distributed (for soil taxa only), mutually exclusive, and independent. The data are representative of other site characteristics. The concepts of statistical estimation, conditional probability, quantified prediction improvement, and selective sorting are applied to use the model in the mapping process. Applications include systematic development of soil‐landscape relationships and legends; documented justification for decisions as to data adequacy, soil interpretations, map unit differentia, variability, and taxonomic descriptions; and increasing accuracy of soil correlation. Programs are standard and widely available.
Significance of Ground Freezing on Soil Bulk Density Under Zero Tillage
Authors: Kay B. D. , Grant C. D. , Groenevelt P. H.
Published: July 2010

Soil bulk densities remain persistently higher in Ontario on soils on which zero tillage is practiced, than on soils which are conventionally tilled. This occurs in spite of the fact that the formation of ice lenses over winter on soils which are frost susceptible may introduce porosity, which is sufficiently large to cause displacements of the ground surface of several centimeters. Studies were carried out over two winter seasons on soils of two different textures and on which two different tillage treatments (conventional and zero tillage) were practiced in order to determine the reason for this anomalous behavior. Soils under zero tillage accumulated more snow over winter and did not freeze as deeply as soils that were plowed in the fall. However the amounts of water which accumulated in the frozen zone were similar per unit depth of frost penetration. The greater depth of frost penetration resulted in significantly greater surface displacement on the fall plowed soil. However the soils under both tillage treatments quickly reconsolidated upon thawing and returned to near prefreezing bulk densities prior to spring planting. The formation of ice lenses appears to create pores which are inherently unstable and collapse as the ice melts and the soil drains. The loss of pores created by ice lenses occurs in a manner analogous to the removal of a slice of meat from between two slices of bread. The unstable nature of pores created by ice lenses appears to be in contrast to the characteristics of pores created by tillage, which on account of their formation by the vertical and horizontal displacement of peds, are more stable.
Effect of Erosion and Landscape Position on the Productivity of Piedmont Soils
Authors: Stone J. R. , Gilliam J. W. , Cassel D. K. , Daniels R. B. , Nelson L. A. , Kleiss H. J.
Published: July 2010

The objective of this study was to determine the effect of past accelerated erosion in the North Carolina Piedmont on soil physical and chemical properties and soil productivity, and to determine the relationship between soil productivity, soil erosion, and landscape position. Data from five Piedmont fields were collected over a 2‐yr period. Within each field, plots were located on all erosion classes and landscape positions present. Definite relationships between erosion class and soil physical and chemical properties were observed. Clay content increased approximately 10% for each erosion class change from slight to moderate to severe. Organic matter content tended to be higher on the more eroded sites. Differences in topsoil depth among erosion classes in a given field ranged from 2.4 to 8.7 cm and the severely eroded areas were always significantly shallower. Available water‐holding capacity of the A horizon (g g−1) always was slightly higher on the more eroded sites. Available P decreased sharply with erosion severity but all sites had levels ≥ 17 g P m−3 which is considered adequate. The highest corn grain yields were usually obtained on the moderately eroded sites as compared to the slightly and severely eroded areas. This was particularly true in 1981 which was a dry year. In a more favorable year (1982) with regard to amount and distribution of growing season rainfall, the yield differences among erosion classes were less. The differences in corn grain yield among landscape positions were much more consistent than yield differences among erosion classes. Those landscape positions that received water from higher elevations produced the highest yields. Because landscape position and erosion severity are not mutually exclusive, we believe that much of the published data dealing with the effects of erosion on soil productivity are confounded by the effect of landscape positions on soil erosion.
Crop‐Water Production Function Model for Saline Irrigation Waters
Authors: Letey J. , Dinar Ariel , Knapp Keith C.
Published: July 2010

The relationship between crop yield and seasonal amount of applied water (crop‐water production function) is required to determine optimum irrigation management. A model is developed for the computation of crop‐water production functions with saline irrigation waters. The model combines three relationships: yield and evapotranspiration, yield and average root zone salinity, and average root zone salinity and leaching fraction. The model allows plant growth adjustment, and therefore evapotranspiration adjustment, to root zone salinity. Crop‐water production functions were computed for tall fescue (Festuca elatior arundinacea L.) for various levels of salinity in the irrigation water. A comparison was made between calculated and published experimentally measured values of leaching fractions and yields of tall fescue grown under conditions of various irrigation water salinities, water application quantities and applied water frequencies. Calculated and measured yields were in good agreement considering the usual degree of variability of field data. Agreement between calculated and measured leaching fractions was not as good as for yields.
Depth of Surface Soil‐runoff Interaction as Affected by Rainfall, Soil Slope, and Management
Authors: Sharpley A. N.
Published: July 2010

The effective depth of interaction (EDI) between surface soil and runoff (the thickness of surface soil in which the degree of interaction is equal to that at the soil surface) was determined for five soils of varying physical and chemical properties under simulated rainfall, in order to quantify the effect of rainfall and soil characteristics on EDI. For all soils EDI increased (1.30–37.43 mm) with an increase in rainfall intensity (50–160 mm h−1) and soil slope (2–20%), although the magnitude differed between soils. The effect of rainfall intensity was attributed to increased runoff energy enhancing mixing in the surface soil and was also a function of soil aggregation. The magnitude of the EDI increase with increasing soil slope was independent of soil type being a function of runoff energy alone. An avg 73% reduction in EDI following the incorporation of 100 kg wheat straw (Triticum aestivum L. sp.) ha−1 and 80% reduction with a 0.5‐mm2 mesh screen, simulating crop cover, was obtained compared to the control (3.36 mm). For all soils the logarithm (ln) of soil loss was linearly related to the ln EDI. This is to be expected since factors affecting EDI (rainfall intensity, runoff energy, and soil aggregation) also influence soil loss. Regression slope of the logarithmic relationship was similar (at the 5.0% level) for all soils, and regression intercept was related to soil aggregation. Thus, EDI and the effect of rainfall and soil management can be estimated from soil loss. This relationship will improve the prediction of adsorbed chemical (P and pesticides) transport in solution, since chemical transport models presently use a fixed EDI value.
Shadecard and Shelterwood Modification of the Soil Temperature Environment
Authors: Childs S. W. , Holbo H. R. , Miller E. L.
Published: July 2010

A study was conducted on steep, south‐facing slopes in southwest Oregon to assess the effect of two common reforestation practices on the soil thermal environment. Three clearcut sites and three shelterwood sites were instrumented to measure soil temperature at five depths in the vicinity of shaded and unshaded Douglas‐fir seedlings. Since the soils studied were skeletal, heat capacities of both fine and coarse soil fractions were determined for each site. These data were used to estimate soil heat fluxes. Shelterwoods decrease soil temperatures approximately 6 K when compared with clearcuts. This result holds at both 20‐ and 320‐mm depths. Shelterwoods also decrease the depth of diurnal heating and decrease maximum hourly heat loss and gain values by 73 and 80 W/m2, respectively. Shadecards, cardboard rectangles placed to the southwest of seedlings, generally have little effect on the soil temperature regime of skeletal soils but are effective in reducing daily heat flux. The dominant shadecard effect is a decrease in average daytime heat flux by 22 W/m2, but shadecards also decrease average nighttime fluxes. Shelterwoods ameliorate seasonal soil temperature conditions significantly and may be an appropriate technique in situations where cumulative soil heating limits reforestation success. Shadecards should be useful in situations where heat stress events of only a few days are a problem. Over a season, shadecards exert little control, and their influence on stress is limited. Since all soils studied had high heat capacities due to large rock fragment content the conclusions of this study may be limited to soils with large soil heat capacity.