bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization and Classification of Seaside—Salt‐marsh Soils on Virginia's Eastern Shore
Authors: Edmonds W. J. , Cobb P. R. , Peacock C. D.
Published: July 2010

Salt marshes, historically, were considered to be of minimal value. Current concepts consider these marshes to have a very high biomass. This study was conducted to characterize soils in seaside salt marshes on Virginia's eastern shore and to classify them according to criteria in Soil Taxonomy and proposed amendments. Results indicate that salt‐meadow marshes, dominantly vegetated by saltmeadow hay (Spartina patens), contain soils with halmyric and nonsulfidic properties and aquic moisture regimes. Classification of these soils as members of the proposed Halmyraqualfs will necessarily broaden the definition of halmyric materials to include an aquic moisture regime and the definition of the argillic horizon to include sodium adsorption ratios (SARs) considerably >13. We propose that soils in these marshes with subsoil illuvial clay accumulations and SARs >13 be classified as members of Typic Natraqualfs even though they lack structure currently defined for natric horizons. Saltmarsh cordgrass marshes, dominantly vegetated by S. alterniflora, contain soils with halmyric and sulfidic properties, silty textures, and peraquic moisture regimes. Tidal mudflats, not vegetated by vascular plants, contain sediments that have halmyric, but dominantly nonsulfidic properties. These results indicate that conditions necessary for the formation and accumulation of sulfide minerals exists in the salt‐marsh‐cordgrass marshes and to a limited extent in the tidal mudflats and in the salt‐meadow marshes. Considerably more information concerning properties of all the soils in the study area is conveyed by the proposed halmyric great groups and subgroups than by taxa currently defined by Soil Taxonomy. Moist incubation of samples provides a convenient and economical method for evaluating soils and sediments as sulfidic materials. Results of this study support the need for the proposed amendments to Soil Taxonomy.
Pedogenesis on the Edwards Plateau, Texas: II. Formation and Occurrence of Diagnostic Subsurface Horizons in a Climosequence
Authors: Rabenhorst M. C. , Wilding L. P.
Published: July 2010

Following reconnaissance efforts to minimize differences in parent materials, 15 pedons were sampled across the Edwards Plateau of Texas, which spans a pronounced moisture gradient. Care was taken to minimize differences in topography by choosing sites on relatively stable landscape positions. Statistically significant positive relationships exist between depth to bedrock or petrocalcic horizon and Thornthwaite's P‐E index. Negative relationships occur between carbonate contents and this index. Petrocalcic horizons are common and most strongly expressed in the dry western part of the study area, while argillic horizons are observed in the more humid eastern portion. High shrink swell activity in the argillic horizons (coefficient of linear extensibility [COLE] values 0.09–0.23) caused difficulty in distinguishing illuvial clay from stress oriented clay, both in the field and in thin section. Well‐oriented illuvial clay was best preserved within interconnected pores of sand and gravel size chert fragments.
Soils of the Mall in Washington, DC: I. Statistical Summary of Properties
Authors: Short J. R. , Fanning D. S. , McIntosh M. S. , Foss J. E. , Patterson J. C.
Published: July 2010

Twenty profiles were examined in each of five transects along the length of the Mall in Washington, DC. The soils were formed in mixed, man‐deposited materials with lithologic discontinuities present in 95% of the profiles. Ninety‐nine percent of the profiles were within fine‐loamy and coarse‐loamy taxonomic families. B horizons were identified in 26% of the profiles based upon colors redder or stronger than those of underlying materials and/or the presence of soil structure, most commonly subangular blocky. Inorganic, manufactured artifacts were present in the particle size control section of 94% of the profiles. The loamy textures were conducive to compaction to high bulk densities of up to 2.03 Mg m−3. Mean bulk density values of 1.61 Mg m−3 for the surface horizon and 1.74 Mg m−3 at 0.3 m were found. The surface horizon had a mean particle density of 2.54 Mg m−3, and the mean particle density at 0.3 m was 2.59 Mg m−3. Pore space was limited, with a mean of 37% at the surface and 33% at 0.3 m. Pore space ranged from 21% to 50%. Data were statistically analyzed according to the position of the horizon from the soil surface. Mean pH of all horizons was 6.2 or higher, and mean pH of the surface horizon was 6.4; however, the pH of 27% of all samples was >7.0. Electrical conductivity was <0.57 dS m−1 in 80% of all surface horizons. Mean organic matter content was 19.7 g kg−1 at the surface, and tended to decrease with depth, although variation in this trend was observed. Mean cation exchange capacity was 11.2 cmol (NH+4) kg−1 in the surface horizon and tended to decrease with depth. Mean base saturation exceeded 88% in all horizons, with Ca as the dominant cation. Elevated levels of heavy metals were observed, with a mean Pb content of 184 mg kg−1 in the surface horizon. Enrichment of other metals was not as pronounced. Statistically fewer samples were required to estimate the mean for physical properties than for chemical properties. Only one sample was needed to estimate the mean particle density within 10% with a 95% confidence interval, whereas over 7000 samples were required to estimate the mean Ni content of the third horizon with a similar confidence interval.
Variability of Runoff and Soil Loss from Fallow Experimental Plots
Authors: Wendt R. C. , Alberts E. E. , Hjelmfelt A. T.
Published: July 2010

The amount of unexplained variation in runoff and soil loss studies often limits the interpretation of data. In this study, variability in runoff and soil loss from 40 essentially uniform experimental plots was examined for 25 natural rainfall events occurring during a 155‐d period. Plots had been maintained uniformly for the prior 3 yr and were kept fallow with periodic cultivation during the study period. Except for events producing low runoff and soil loss, event coefficients of variation were relatively constant for both runoff and soil loss at about 20%. Differences in runoff and soil loss among plots varied with event. Only minor amounts of observed variability could be attributed to any of several measured plot properties, and plot differences expressed by the 25 events did not persist in prior or subsequent runoff and soil loss observations at the site. The relatively large amount of unexplained variability shows that several replications of treatments are needed to confidently estimate mean runoff or soil loss for comparison purposes and that effects of factors having relatively minor effects on runoff or soil loss may be difficult to detect statistically. The fact that most variability is unexplained indicates important effects of factors or processes that are not currently understood.
Agronomic Potential of Eleven Phosphate Rocks from Brazil, Colombia, Perú, and Venezuela
Authors: Léon L. A. , Fenster W. E. , Hammond L. L.
Published: July 2010

The agronomic potential of 11 South American phosphate rocks was estimated by four laboratory methods (neutral ammonium citrate with two extractions, acid ammonium citrate [pH 3], 2% citric acid, and 2% formic acid) and by crop response data obtained from a greenhouse experiment with guinea grass (Panicum maximum Jacq.) on an acid (pH 4.9) Tropeptic Haplustox (Las Gaviotas) from Colombia. Standards for comparison included triple superphosphate (TSP) and phosphate rocks from the USA (North Carolina, central Florida, and Tennessee), Tunisia (Gafsa), and Israel (Arad). The relationship between laboratory reactivity values and crop response was evaluated following three cuttings of guinea grass at four rates of P application. Almost no yield was obtained without added P, and significant differences were observed between response curves of the P sources. Based on both solubility as measured by the four methods identified and crop response data, the 11 phosphate rocks were found to be segregated into four groups representing high (Bayovar), medium (Huila and Pesca), low (Sardinata, Patos de Minas, Lobatera, Araxá, and Abaeté), and very low (Catalão, Jacupiranga, and Tapira) reactivity. Solubility in neutral NH+4 citrate was found to be the most accurate of the chemical procedures tested. The relationship between yield and source solubility in neutral NH+4 citate showed that all of the sedimentary sources were more reactive than the igneous or metamorphic sources.
Influence of Thiosulfate on Nitrification of Ammonium in Soil
Authors: Janzen H. H. , Bettany J. R.
Published: July 2010

Ammonium thiosulfate, a common nitrogen (N) and sulfur (S) source in fluid fertilizer formulations, has been reported to inhibit soil nitrification processes. A laboratory study was established to determine the degree and persistence of the inhibitory effect and to examine the agronomic potential of thiosulfate as a nitrification inhibitor. Thiosulfate applied to the soil was rapidly oxidized with a temporary accumulation of tetrathionate. The formation of nitrate (NO‐3) from applied ammonium (NH+4) was markedly suppressed at higher rates of applied thiosulfate. At the highest rate of thiosulfate application (100 mg S kg−1), relative inhibition of NO‐3 production over 22 d was 55% as compared to 57% for nitrapyrin, applied at 2 mg kg−1. Unlike nitrapyrin, thiosulfate inhibited the second nitrification reaction, the oxidation of nitrite (NO‐2) to NO‐3, and resulted in the accumulation of NO‐2 at concentrations as high as 42 mg N kg−1. This accumulation of NO‐2 may represent a serious drawback to the use of ammonium thiosulfate as a nitrification inhibitor under some conditions since NO‐2 is known to be toxic at relatively low concentrations.
Calcium‐Magnesium Exchange on Illite in the Presence of Adsorbed Sodium
Authors: Sposito Garrison , LeVesque C. S. , Hesterberg Dean
Published: July 2010

Binary and ternary cation exchange experiments were performed with Na+, Ca2+, and Mg2+ on Silver Hill illite and on a soil illite suspended in 50 mol m−3 perchlorate at pH 7. The binary experiments indicated no preference for Ca over Mg on the specimen illite, but selectivity for bivalent cations over Na+ and for Ca2+ over Mg2+ on the soil illite. The ternary exchange data showed that, for both illites, there was no effect of adsorbed Na on the Ca‐Mg exchange isotherm at exchangeable sodium percentages from 0 to 30%, either for freshly‐prepared clay suspensions or for those aged up to 270 d in NaClO4. No significant differences in the total adsorbed metal charge (Qo) were observed among the binary and ternary exchange experiments, and Qo was independent of the degree of bivalent cation saturation (ECa or EMg) in the Na → Ca and Na → Mg exchange experiments on the soil illite. The Vanselow selectivity coefficient for Mg → Ca exchange on the soil illite decreased as ECa increased, showing a plateau near ECa ≈ 0.6 and dropping to 1.0 as ECa became equal to 1.0. This behavior was interpreted as evidence for at least two classes of surface complex involving Ca and Mg.
Comparison of Several Lime Requirement Methods on Coarse‐textured Soils of Northeastern Nebraska
Authors: Alabi K. E. , Sorensen R. C. , Knudsen D. , Rehm G.W.
Published: July 2010

Soils of the eastern Sandhills of Nebraska are becoming progressively more acid as a result of the development of irrigation and subsequent use of high N fertilizer amounts for corn (Zea mays L.). Chemical determinations of lime requirement are expected to vary in their applicability to these poorly buffered, sandy soils. The objective of this research was to compare the abilities of selected chemical methods of determination of lime requirement to predict lime needs of sandy soils. The lime requirement values of 74 acid sandy soils from northern Nebraska were determined by eight methods. Correlation and regression were used to compare these values with those obtained by incubating the soils with varying amounts of lime in the laboratory. The validity of the CaCO3 incubation method as a standard method was confirmed by a Ca(OH)2 titration procedure. Most of the soils studied required <4492 kg of lime ha−1 to attain soil pH 6.5. The relationship between the values from chemical determination of lime requirement with those from incubation were essentially linear for all methods. Although the nature of the relationship as expressed in the intercepts and slopes of the regression curves and the precision varied among methods, values from all methods were correlated with lime requirement values from incubation. Determination of the correlations among methods showed that lime requirement values for each method were highly correlated with those from every other method included in the study. Correlation studies of lime requirement values for five methods with selected soil properties showed that no single property was correlated with all methods. However, soil pH, clay content, cation exchange capacity, and Mn and Al contents were correlated with values from at least one method.
Effects of Soil Moisture on Soil pCO2, Soil Solution Bicarbonate, and Iron Chlorosis in Soybeans
Authors: Inskeep William P. , Bloom Paul R.
Published: July 2010

Four pot experiments were performed with five calcareous soils from western Minnesota (Haplaquolls and Calciaquolls) to determine the effects of soil moisture and soil temperature on Fe chlorosis in soybeans [Glycine max (L.) Merr.]. We used a factorial design with gravimetric moisture contents and bulk density values ranging from 0.22 to 0.44 kg kg−1 and 1.14 to 1.38 Mg m−3, respectively. Factor combinations of these levels resulted in ranges of volumetric moisture contents from 0.27 to 0.54 m3 m−3, air filled porosity fractions from 0.27 to 0.00, and soil matric potentials from <‐1500 to near 0 kPa. The soil pCO2 contents measured from gas wells in pots increased from 0.16 to 1.64 cmol mol−1 as a result of decreased gas diffusion when the air‐filled porosity decreased. With increasing soil moisture, soil solution HCO‐3 concentrations attained values as high as 10 mM. Total chlorophyll (ChlT) contents of Anoka soybeans decreased as soil moisture, soil pCO2, and soil solution HCO‐3 increased. The same response was not observed in all calcareous soils. Calcareous soils with lower amounts of clay sized CaCO3, lower soil solution Mg2+, and/or lower bicarbonate extractable P did not produce as severe a chlorosis with increased moisture. This suggests that clay sized CaCO3, Mg, or P may be additional stress factors associated with HCO‐3 induced chlorosis. High soil moisture treatments on a calcareous soil provided an effective soil screen for differentiating between susceptible and nonsusceptible soybean cultivars. Soil temperatures of 12 and 26°C produced more chlorosis at a given soil moisture than at 16 or 19°C. Soil temperature appears to be an additional stress factor, which might explain some of the variability in the incidence of Fe chlorosis under field conditions.
Statistical Evaluation of the Taxonomic Composition of Three Soil Map Units in Virginia
Authors: Edmonds W. J. , Lentner M.
Published: July 2010

A consociation map unit is usually characterized by its central concept selected on the basis of mapping experience, by defining the central concept using morphological and laboratory data, and by assuming that ranges of soil properties defined for the taxon that encompasses the central concept and taxa that includes similar soils represent ranges delineated by the map unit. This study was conducted to statistically evaluate the dominant taxon or central concept as an indicator of map unit purity. Results indicate that the central concept of one of three map units studied had confidence intervals (CIs) that did not exceed limits defined for more than one taxon. Numbers of samples needed for 50% assurance of estimating means within 10% of their true value exceeded cost and time constraints for current soil characterization programs. Of the three map units studied, the highest probability of observing the stated composition was about 0.3 or 30% of the time. Therefore, descriptions of the patterns of occurrence of soils and observed ranges of properties within map units appear to provide more appropriate bases for predicting responses of soils to use and management for the three map units studied.
Simulation and Measurement of Evaporation from a Bare Soil
Authors: Lascano R. J. , van Bavel C. H. M.
Published: July 2010

A numerical model was used to simulate evaporation, water, and temperature profiles for a bare soil over drying cycles of 8, 9, and 20 d using soil hydraulic characteristics and meteorological data as input. The model was also used to evaluate the effect of the thickness of the surface layer in the model on the simulated evaporation rates. The simulated values were compared to actual measurements made over the same period of time. The model predicted cumulative evaporation within 1 standard deviation (SD) of the measured values, and in 34 of 37 cases, predicted daily rates also within 1 SD of the measured means. The predicted water and temperature profiles were within 1 SD of the means measured. The accuracy of the model was further confirmed by its ability to predict soil surface temperature within 1.0°C and net radiation within 40 W/m2 of the measured values. The sensitivity of the simulated evaporation rates to the assigned thickness of the surface layer suggested that a value of 0.005 m was adequate under the conditions in which the model was tested. Hence, we conclude that the model is accurate to predict bare soil evaporation rates, as well as soil water and temperature profiles.
Analysis of Water Flow from Cylindrical Macropores
Authors: Smettem K. R. J.
Published: July 2010

Water flow from cylindrical macropores of finite length is predicted using an approximate analysis derived previously for flow from a steady constant‐head uncased borehole permeameter in homogenous unsaturated soil. This analysis is appropriate in cases where the macropores fill rapidly and remain completely water filled. Under these conditions predicted macropore flow rates compared well to those obtained from measurements of flow into both “artificial” and natural macropores. The study emphasises the effect of pore continuity, with pore length exerting a dominant influence on the magnitude of macropore volume fluxes over the range of macropore diameters commonly encountered in agricultural soils.
Effects of Redox on Zinc Deficiency in Paddy Rice
Authors: Sajwan K. S. , Lindsay W. L.
Published: July 2010

Greenhouse and laboratory experiments were conducted to determine if the pH and redox relationships associated with various soil moisture conditions could help to explain the increased incidence of Zn deficiency of rice (Oryza sativa L.) in submerged soils through greater solubilization of Fe and Mn. The soil used in these studies was Sycamore loam (Aeric Haplaqucepts). Increasing the moisture content of soils increased Fe and Mn concentration and decreased that of Zn in the plant tissue. Application of Zn increased Zn concentrations and decreased those of Fe and Mn in plant tissue. Depth and duration of flooding affected both pH and redox (pe + pH). After 20 days of continuous flooding, pH approached 7.0 and pe + pH approached to 4.0 at 2 cm below the soil‐water interface. Both pH and pe + pH decreased significantly with soil depth, reflecting greater accumulation of CO2 and depletion of O2. With alternate flooding and drying the pH fluctuated from 8.0 during drying to near 7.0 during flooding while pe + pH fluctuated from 15.0 during drying to approximatelyy 6.0 during flooding. Under controlled redox conditions in the laboratory, decreasing pe + pH from 14.99 to 4.00 decreased the Zn content of rice plants from 39 to 9 mg kg−1 while the contents of Fe increased from 140 to 339 and that of Mn from 226 to 919 mg kg−1. The findings reported herein support the hypothesis that Zn deficiency observed in the submerged paddy rice in this study can be partially explained by increased reduction and solubilization of Fe and Mn which had an antagonistic effect on the availability and uptake of Zn. It is also possible that increased HCO‐3 may also contribute to increased Zn deficiency. It is hypothesized that Fe dissolved at reduced microsites and subsequently reprecipitated as ferrosic hydroxide (Fe3[OH]8) in more oxidized zones. The higher solubility of Fe maintained by Fe3(OH)8 could depress Zn2+ solubility through formation of ZnFe2O4 or a similar franklinite‐like solid material.
Orthophosphate Solubility Transformations and Availability from Dual‐Applied Nitrogen and Phosphorus: Calcareous Soil
Authors: Hanson R. L. , Westfall D. G.
Published: July 2010

Higher extractable P levels resulting from dual application (DApp) of ammoniacal‐N and ammonium polyphosphate (APP) have been postulated to be a function of pH changes in the fertilizer injection zone of acid to neutral soils. The objective of this study was to characterize the injection zone of DApp of NH4OH (to simulate NH3 application) and APP to a pH‐buffered calcareous soil (Weld sc1; Aridic Paleustolls). A previously studied acid soil, (Ascalon s1; Aridic Argiustolls), was used for comparison. The APP was applied to potted soil either alone or in DApp with NH4OH. The injection zone soils were sampled through time and analyzed for P solubility and NaHCO3‐P. Solubility of P remained constant or increased up to 10 d after application of DApp of APP and NH4OH to the calcareous soil. This treatment also enhanced NaHCO3‐P levels. Increased P solubilities and NaHCO3‐P levels were associated with slight pH decreases in the calcareous soil. This change in pH is postulated to be due to nitrification of the ammoniacal‐N; microsite pH change is undoubtedly much greater than what was measured in the whole soil mass and probably influenced P availability and solubility substantially.
Soil‐geomorphic Evolution of a Boroll Catena in Southwestern Alberta
Authors: Pennock D. J. , Vreeken W. J.
Published: July 2010

The geomorphic and pedological processes that have influenced the development of a Boroll catena in south‐western Alberta are examined using a combination of sedimentological and pedological techniques. Four geomorphic episodes are responsible for the sediments in the catena: the deposition of glacial till, two colluvial episodes, and a final eolian episode that deposited a thin mantle of sediment over the landscape. The vertical and lateral distribution of grain size fractions in the landscape is largely the result of these geomorphic processes. The vertical distributions of Fe and CaCO3 show some relict features from earlier phases of pedogenesis, whereas the organic C values appear to be related only to the present configuration of the landscape.
Measurement of Force vs. Time Relations for Waterdrop Impact
Authors: Nearing M. A. , Bradford J. M. , Holtz R. D.
Published: July 2010

Force vs. time relationships of waterdrop impact are important for understanding the process of erosion caused by soil splash. Waterdrop impact forces were measured for 3.31‐, 3.83‐, 4.51‐, and 5.25‐mm diam drops falling from a height of 14.0 m onto piezoelectric transducers with rise times of 2 and 5 µs. Peak forces occurred within 13 to 21 µs of initial contact, ranged from 1.0 to 3.8 N, and decreased to 0.5 N after approximately 100 µs. Average pressures under impact were calculated from the force measurements and an approximateion of waterdrop contact area as a function of time and decreased to 100 kPa after 50 µs. The results indicated that the times and magnitudes of the force of impact were poorly predicted from currently used models and that the compressional wave generated in the water upon impact is probably an important parameter in determining the level and time distribution of forces during impact.
The Influence of Pretreatment Forest Soil Variability on Interpretation of Posttreatment Results
Authors: Slay J. Melinda , Lockaby B. G. , Adams J. C. , Vidrine C. G.
Published: July 2010

Analysis of covariance procedures were used to evaluate differences in forest soil chemical properties among four site preparation techniques. Comparisons were made between analyses of variance adjusted with pretreatment soil chemical data used as covariates and unadjusted analysis of variance results. These comparisons indicated that failure to adjust for pretreatment spatial variation in soil chemical properties would lead to misinterpretation of the study results. This misinterpretation involved different rankings (for unadjusted vs. adjusted) of the site preparation treatment effects on soil N, P, K, Ca, and Mg concentrations.
X‐ray Photoelectron Studies of Anion Adsorption on Goethite
Authors: Martin Ronald R. , Smart Roger St. C.
Published: July 2010

X‐ray photoelectron spectroscopy (XPS) was evaluated as a technique to study anion adsorption on soil minerals; in this case, the well‐characterized systems of phosphate, sulfate, and selenite adsorption on goethite (α‐FeOOH). X‐ray photoelectron spectroscopy measured directly the surface coverage, the form of the adsorbed species and substrate, and the pH dependence of adsorption. The results confirm the previously reported adsorption mode in which two A‐type hydroxyls are replaced by coordination of two of the oxygen atoms of the anion.
A Sensitive Colorimetric Method for the Quantitation of Selenite in Soil Solutions and Natural Waters
Authors: Holtzclaw Kenneth M. , Neal Rosemary H. , Sposito Garrison , Traina Samuel J.
Published: July 2010

A sensitive colorimetric method for the quantitation of selenite in aqueous solution at concentrations between 0.15 and 30 µmol kg−1 was developed. The method is based on the formation of a colored complex between selenite and 2,3‐diaminonapthalene (DAN) and is selective for selenite in selenite‐selenate mixtures. The yellow color of the complex is stable for at least 48 h and there appear to be no interference effects from selenate, sulfate, and other normal soil solution ionic constituents at moderate to high concentrations. Because the method is specific for selenite, it can be combined with acid digestion and hydrolysis to quantitate total Se and to speciate Se in soil solutions containing both selenite and selenate.
Nonexchangeable Ammonium Nitrogen Contribution to Plant Available Nitrogen
Authors: Baethgen Walter E. , Alley M. M.
Published: July 2010

Recent European research has shown that nonexchangeable NH+4‐N may be released from soil and utilized by crops. Surface and subsoil samples were collected from agriculturally important soils of Coastal Plain, Piedmont, and Ridge and Valley regions of Virginia to determine the relative importance of different soil N fractions for supplying N to wheat (Triticum aestivum L. em Thell) grown in the greenhouse. Exchangeable and nonexchangeable NH+4‐N, NO‐3‐N, total N, organic matter contents and an index of organic N availability were measured on all samples. Plant available N was measured by N uptake of successive wheat crops grown in the greenhouse. Multiple linear regression models for different groups of samples were used to determine the significance of the different soil N fractions to the plant available N supply, and to predict N uptake by wheat. Best models were selected considering fit, significance of the regression coefficients, and predictive ability. Collinearity effects on the models were reduced by using Principal Components regression. All the soils provided significant amounts of N to the wheat in both the first and second crops. Exchangeable NH+4‐N and NO‐3‐N were the major initial sources of plant available N. Nonexchangeable NH+4‐N contents were highest in fine‐textured soils, and/or soils with large amounts of previously‐added N fertilizers. This soil N fraction was a significant contributor to the plant available N supply for all soil groups, and amounts up to 129 mg kg−1 soil were measured. Interaction of nonexchangeable NH+4‐N with readily‐available N was found in all soil groups. Nonexchangeable NH+4‐N should be considered as a potential plant available N source in future research.
Greenhouse Evaluation of Elemental Sulfur and Gypsum for Flooded Rice
Authors: Chien S. H. , Hellums D. T. , Henao J.
Published: July 2010

Recently, S deficiency has become a problem in many flooded soils for rice (Oryza sativa L.) production because of the increased use of high‐analysis of N and P fertilizers that do not contain S. The objective of this study was to compare the relative agronomic effectiveness (RAE) of powdered elemental S and urea‐S melt (prilled or powdered) to that of gypsum in a pot trial using an S‐deficient Josephine soil (fine‐loamy, mixed mesic, Typic Haplozerults). The RAE value of powdered elemental S for grain yield was 78% with respect to gypsum when both fertilizers were surface broadcast onto the soil surface at rates up to 40 mg S kg−1. Prilled urea‐S melt was found to be significantly less effective than powdered urea‐S melt in terms of increasing rice grain yield at a rate of 20 mg kg−1. Placement of urea had no effect on rice response to elemental S for a given S placement method. The various S placement methods demonstrated the following order of agronomic effectiveness of elemental S: surface broadcast = incorporation > deep placement. Rice response to gypsum, on the other hand, was found to be the same, irrespective of placement method. Prilled urea‐S melt was approximately 61% as effective as gypsum in increasing rice grain yield when incorporated into the soil at 20 mg S kg−1.
Chemical Properties of the Rhizosphere in an Acid Subsoil
Authors: Kirlew Peter W. , Bouldin David R.
Published: July 2010

A method of corn seedling culture was developed which allowed growth of the root systems in samples of an acid subsoil (pH 4.7‐5.0) for at least 2 weeks after seedling emergence, without adding additional water to the subsoil. This method was used to culture corn inbred and corn hybrid seedlings in samples of acid subsoil in two separate greenhouse studies. Bulk (non‐rhizosphere) soil and rhizosphere soil samples obtained in these studies were assayed for pH, KCl‐extractable Ca, KCl‐extractable Al, and water‐extractable Ca. The pH of rhizosphere samples was less than that of the bulk samples for all inbreds and hybrids. This pH decrease was 0.16 in one experiment with inbreds, and 0.11 in another experiment with hybrids. In comparison to the bulk soil, the rhizosphere soil contained 0.16 cmolc kg−1 more KCl‐extractable Al, 0.13 cmolc kg−1 less KCl‐extractable Ca, 0.023 cmolc kg−1 more water‐extractable Ca, and 0.10 cmolc kg−1 less total Ca. The difference in the sum of KCl‐extractable Al plus Ca between bulk and rhizosphere soils was not statistically significant. The results of both studies are consistent with the hypothesis that Ca uptake by the root depleted the Ca in the rhizosphere, that H ions were released by the root in response to excess cation (vs. anion) uptake and that this excess H+ dissolved basic Al compounds, which increased the KCl‐extractable Al. The lack of statistically significant differences between rhizosphere and bulk soil parameters among hybrids/inbreds indicate that differential pH changes in the rhizosphere are not the chief mechanism of any differential Al tolerance among these corn inbreds and hybrids.
Effect of Parent Rocks on Chemical and Mineralogical Properties of Some Oxisols in Brazil
Authors: Curi N. , Franzmeier D. P.
Published: July 2010

A toposequence of soils developed primarily from basalt in the Central Plateau of Brazil and a pedon developed primarily from itabirite (a hematite‐quartz metamorphic rock) were studied in the Quadrilatero Ferrifero. The itabirite‐derived Oxisol consists almost entirely—900 to 950 g kg−1 (90‐95%)—of Fe oxides and oxyhydroxides, compared with 250 to 300 g kg−1 in the basalt‐derived Oxisol. The soil on itabirite also has coarser particle size, higher particle density, and somewhat lower surface area. It lacks kaolinite and gibbsite but contains more goethite and has greater magnetic susceptibility. It also is much lower in all essential plant nutrients (except Fe and P), and much lower in several non‐nutrient minor elements as well. Magnetite grains in basalt are relatively abundant in minor elements which could be released slowly during mineral weathering. The effect of the parent material is still evident even in highly weathered soils, indicating the need for the separation between itabirite‐ and basalt‐derived Oxisols in a system of soil classification. In itabirite‐derived soils the Fe2O3/TiO2 ratio (H2SO4 digestion) is >16 and the magnetic susceptibility of the whole soil is > 189 × 10−6 m3 kg−1 (15 000 × 10−6 cgs). These limits of soil properties reflect the original parent material and could be the differentiating characteristics in soil classification systems. Particle density, amount of trace elements, and capacity to fix phosphorus are accessory properties associated with the differentiating characteristics.
Soil Property Comparisons in Virgin Grasslands Between Grazed and Nongrazed Management Systems
Authors: Bauer Armand , Cole C.V. , Black A.L.
Published: July 2010

Soil organic C and total N contents of grazed virgin grasslands have been used as the comparison standard to assess the change in soil organic matter (OM) generated by cultivation in the Northern Great Plains. The assumption has been that grassland soil properties were not altered by livestock grazing and therefore reflect the native grassland condition at the time man began cultivating for crop production. In this study, soil properties of grazed and nongrazed (relict) virgin grasslands are compared to assess the effect of grazing. Four sites each of moderately coarse‐, medium‐, and fine‐textured soils under grazed and under relict management were sampled at 0‐ to 0.076‐, 0.076‐ to 0.152‐, 0.152‐ to 0.305‐, and 0.305‐ to 0.457‐m depths. Analyses were made to compare organic C, total N, total P, organic P, and inorganic P contents, and bulk density between the management systems. Nutrient contents differed between the two management systems.

The largest content was not exclusively associated with either system; neither was the difference the same among textural groups or sampling depth. When averaged over all soil textures and depths, organic C and total P contents showed opposite trends from total N. Organic C and total P contents to 0.457 m were larger in relict grasslands by about 1.27 and 0.029 kg m−2, respectively, while the total N content was larger in grazed grasslands by about 0.163 kg m−2. Since the fencing of grasslands for livestock control about 75‐yr ago, differences between the two systems have developed at an average annual rate of about 165 kg C, 20 kg N, and 4 kg P ha−1. Bulk densities were highest in grazed grassland in the uppermost 0.076 m. Based upon the organic C and total N contents in relict grasslands, reported losses of OM resulting from cultivation have been either over‐ or under‐estimated, depending on whether organic C or total N content in grazed grasslands has been used as the comparison standard.
Dependence of “True” Surface Energy of Soils on Air Entry Pore Size and Chemical Constituents
Authors: Hadas A.
Published: July 2010

Stability and strength of soil structure depend on soil constituents and the manner in which they interact with each other. Some constituents, such as CaCO3, organic matter (OM), and Fe oxide act as cementing agents. Soil structure strength dependence on those soil constituents was studied. Apparent and “true” surface energy of a soil was defined as the amount of energy required to produce a new unit of surface area or propagate a crack, respectively. These energy values were determined by modifying Sack's (1946) and Griffith's (1924) theory to data obtained from brittle fracture tests on molded soil samples from 16 soils varying in clay, OM, CaCO3, and Fe2O3 contents. A negative linear relationship between the apparent surface energy and the pore radius at air entry was found. No distinct relationship was found between the “true” surface energy of the soils and the contents of CaCO3 and Fe oxide. An inverse relationship was found between “true” surface energy and cation exchange capacity. Possible new research directions are discussed in view of the data presented.
Root Density, Abundance, and Distribution in the Mixed Mesophytic Forest of Eastern Kentucky
Authors: Kalisz P. J. , Zimmerman R. W. , Muller R. N.
Published: July 2010

Root density, abundance, and distribution to bedrock or to the 150‐cm depth were measured in 40 soil profiles spanning a species compositional gradient. Profile morphology was relatively uniform for the soils examined. Root density (LV; length per unit soil volume) was not related to bulk density or coarse fragment percentage within individual sampling depths, and decreased exponentially from ranges of 18200 to 35900 m m−3 in the 0‐ to 5‐cm depth, to 400 to 700 m m−3 in the 100‐ to 150‐cm depth. LV in the upper 100 cm of soil was highest under oak‐dominated forests on the xeric sites, averaging ∼ 60% greater than transitional or beech stands. Root abundance (LA; length per unit ground surface area) was not related to profile depth, and increased along the gradient from mesic to xeric forests. Total profile LA averaged 5800, 6400, and 10000 m m−2, respectively, under beech (Fagus grandifolia), transitional (primarily, Carya spp., Quercus rubra, and Liriodendron tulipifera), and oak (Quercus spp.) forests. LA in both Oe and mineral soil horizons increased in the order beech < transitional < oak. On the average, 17% of the root length occurred in the Oe horizon, 26% in the A horizon, and 90% within the solum to a depth of ∼ 65 cm. Variations in LV and LA across the species compositional gradient are most simply interpreted as species adaptations to sites with differing moisture regimes.
Significance of Sulfide Oxidation in Soil Salinization in Southeastern Saskatchewan, Canada
Authors: Mermut A. R. , Arshad M. A.
Published: July 2010

Several deep soil columns in the Weyburn area, Saskatchewan, Canada, show features related to S2‐ oxidation, including the presence of high amounts of SO2‐4 salts and low pH. A soil 4‐km west of Cedoux that had 1‐m layer of till underlain by Cretaceous marine shale was selected to characterize these features. X‐ray diffraction, scanning electron microscope, and chemical techniques confirmed the presence of well‐developed crystals of natrojarosite between the 100‐ to 600‐cm depth, and sulfides below 550 cm. Sulfate was the predominant water‐soluble anion, with Na+ followed by Mg2+ and Ca2+ as major cations. Accumulation of sulfate in the Cedoux soil and similar soils in the area was attributed to sulfide oxidation and hydrolysis of natrojarosite. Sulfate salts probably are still produced at present. Due to their mobility and recycling in the soils and Cretaceous marine shale it was difficult to bring to light the genesis of salts in Saskatchewan.
Use of Soil‐profile Sulfate Data for Predicting Crop Response to Sulfur
Authors: Hue N. V. , Cope J. T.
Published: July 2010

Sulfur deficiencies in early growth stages do not always result in final yield reduction in many crops. This suggests a greater contribution of subsoil sulfate (SO4) and/or of S mineralization later in the season to the S requirements of plants. The subsoil SO4 contribution should be assessed in order to develop a method that can reliably predict crop response to S. A greenhouse experiment was conducted with various combinations of topsoil (0‐20 cm layer) and subsoil (20‐60 cm layer) materials from a Hartsells series (Typic Hapludult) where crop response to S had been observed, and a Benndale series (Typic Paleudult) where there was no response to S in field experiments. By determining soil SO4 depletion in each layer by crops of grain sorghum (Sorghum bicolor L. Moench.), it was extimated that plants derived approximately 0.55 of their S need from the surface 0 to 20 cm, and the remaining 0.45 from the subsoil. Subsequently, a weighted concentration of soil SO4 for the entire profile was calculated; and values of 13.8 mg S kg−1 for extractable SO4 and 0.25 mM for soil‐solution SO4 were the minimum concentrations above which no crop response to S is expected. The use of weighted means of soil‐profile SO4 data correctly predicted yield responses to S of soybeans (Glycine max L. Merr.), corn (Zea Mays L.), and sorghum in a field experiment, which were previously unexplained based on SO4 concentrations of the surface soil.
The Effect of Calcium and Magnesium on Soil Nitrate Determination by Automated Segmented‐flow Methods
Authors: Ananth S. , Moraghan J. T.
Published: July 2010

An automated procedure, involving the reduction of NO‐3 to NO‐2 by an alkaline solution of hydrazine sulfate containing traces of Cu2+, is commonly used for determination of small quantities of NO‐3‐N in electro‐ultrafiltration (EUF) extracts of soils. When this reduction method was employed to determine NO‐3‐N in aqueous extracts from certain Calciaquolls, low and erratic results were obtained with 24 of 46 soil samples. The problem extracts contained high levels of Ca2+ and Mg2+ that interfered with the method. Soil extracts with <40 mg Ca2+ L−1 and 15 mg Mg2+ L−1 presented no analytical problems. Placement of a cation exchange resin column between the sampler and pump of a Technicon AutoAnalyzer II overcame the interference, due presumably to removal of Ca2+ and Mg2+ from the flow line. Solution studies revealed that Ca2+ and especially Mg2+ prevented quantitative reduction of NO‐3 to NO‐2. No analytical problems were encountered with any of the soil extracts when a Cd‐Cu column was used to reduce NO‐3 to NO‐2. Any hydrazine sulfate reduction method should be carefully evaluated when newly introduced as an analytical procedure for soil NO‐3‐N determination.
The Stable Isotope Chemistry of a Native and Irrigated Typic Natrargid in the San Joaquin Valley of California
Authors: Amundson Ronald G. , Lund L. J.
Published: July 2010

The stable C and O isotope chemistry of native and irrigated Typic Natrargids was examined in order to determine the relationship between the climate and vegetation and the δ13C and δ18O of the native pedogenic carbonates (CaCO3) and the effect of irrigation on the CaCO3 in the cultivated soils. The native soil had a sparse vegetative cover consisting of grasses and salt tolerant shrubs, especially Atriplex polycarpa (Torr.), S. Wats. The δ13C of the CaCO3 reflected the mixture of C3 and C4 vegetation and the δ18O of the CaCO3 suggested that it had formed from soil H2O that had undergone extensive amounts of evaporation. At the time of sampling, alfalfa (Medicago sativa L.) was being grown on the irrigated soils. These soils had CO2 partial pressures of up to 7 KPa, nearly 20 times that of the native soil. The δ13C of the CaCO3 in the irrigated soils was not significantly different than that of the native soils which was due, in part, to the relatively small isotopic difference between the newly formed CaCO3 in the irrigated soil and much of that which occurred naturally. However, the δ18O of CaCO3 in the irrigated soils appeared to be shifted to more negative values than the δ18O of the native CaCO3. Based on the differences in the δ18O of the CaCO3 in the irrigated and native soils, it was semiquantitatively estimated that between 10 to 40% of the carbonate in the irrigated soils was newly formed or had dissolved and reprecipitated as a result of irrigation, increased biological activity, and the application of chemical amendments.
Cumulative Effects of Simulated Acid Rain on Soil Chemical and Microbial Characteristics and Conifer Seedling Growth
Authors: McColl J. G. , Firestone M. K.
Published: July 2010

Effects of simulated acid rain treatments of HNO3 and H2SO4, in the mole ratio of 3:1 and pH 5.6, 4.5, 4.0, and 3.0, were tested on seedlings of Douglas‐fir (Pseudotsuga menzesii [Mirb.] Franco), sugar pine (Pinus lambertiana Dougl.), and ponderosa pine (Pinus ponderosa Laws) growing in A‐horizon samples of two forest soils. Two wet periods of 34 and 27 weeks duration, separated by a dry period of 18 weeks, simulated climatic conditions common in the Sierra Nevada, California. Representative results are presented for soil supporting Douglas‐fir, plus results of growth and shoot‐N for all three species. Effects differed between soils but were usually increased from one wet period to the next, and markedly decreased with soil depth. Effects commonly appeared in the pH 3.0 treatment only. Little or no effects were noted for seedling growth, visual symptoms of foliar damage, N concentration in shoots, or for the general soil microbial assays of CO2 evolution and microbial biomass. There were notable decreases in exchangeable cations and soil pH, and increases in soil Al, Mn, Fe, and Zn. Effects on N transformations in soil were inconsistent, but in the pH 3.0 treatment there were some significant increases in mineralizable N and denitrification potential, and decreases in nitrification potential. Similar results were obtained for N transformations in one of the same forest soils supporting ponderosa pine in an earlier experiment of only 12 weeks duration, but at greater acidity of pH 2.0.
Occurrence of High‐charge Beidellite in a Vertic Haplaquoll of Northwestern Minnesota
Authors: Badraoui M. , Bloom P. R. , Rust R. H.
Published: July 2010

The 2:1 layer silicate mineralogy of a Vertic Haplaquoll of north‐western Minnesota was studied using x‐ray diffraction and determination of cation exchange capacity (CEC). The x‐ray diffraction behavior of Li‐ and K‐saturated samples demonstrated that a highcharge smectite with tetrahedral charge dominates the mineralogy of both the coarse and the fine clay fractions. The high CEC and the large difference between Li‐CEC and K‐CEC confirmed the x‐ray results. Alkylammonium‐clay complex basal spacings show two phases of 2:1 clays; a high charge (about 0.9 molc per ½ unit cell formula) phase concentrated in the coarse clay and an Fe‐rich beidellite with a charge of 0.4 to 0.5 molc per ½ unit cell formula. The high charge phase largely represents K+ ‐depleted mica formed during the analytical procedure. This phase may also contain some soil vermiculite. The results presented in this study suggest that beidellite is a product of mica weathering, and that during weathering soil mica is transformed first to a vermiculite then to a beidellite, preserving the tetrahedral character of the charge.
Thermodynamic Evaluation of Amorphous Aluminosilicate Binding Agents in Fragipans of Western Kentucky
Authors: Karathanasis A. D.
Published: July 2010

Composition of soil solutions in contact with fragipan and nonfragipan horizons of Fragiudalfs in western Kentucky were related to the composition of soil amorphous constituents removed by various extractants. Increased amorphous Si/Al ratios in fragipan horizons were correlated well with reduced pH4SiO4 solute functions. A Si‐rich amorphous aluminosilicate precipitate of the general formula [Al(OH)3](1 − x) [SiO2]x and with a molar fraction ranging from 0.55 to 1.00 is proposed to account for the rigidity of the fragipan horizons. Similar free Al‐rich amorphous aluminosilicate precipitates are suggested to control Al and Si activities in solutions of nonfragipan horizons with pH >4.5. Silica and Al activities of soil solutions with pH <4.5 are consistent with the solubility of crystalline soil minerals. The amorphous aluminosilicate precipitates are considered to be weathering products of feldspar dissolution reactions. The composition, solubility, and rigidity of the amorphous aluminosilicate precipitates are believed to be controlled by conditions of loess deposition and drainage. Iron, Mg, and Na appear to make only minor contributions to the binding amorphous aluminosilicate agent, with Na having the most active involvement in the cementation process.