bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Rothmund‐Kornfeld Description of Cation Exchange
Authors: Bond W. J. 
Published: July 2010

AbstractSimple descriptions of cation‐exchange isotherms are required to permit interpolation and extrapolation from a limited data set. Conventional thermodynamic approaches do not result in simple expressions in terms of a small number of measurable constants. The empirical Rothmund‐Kornfeld power function approach has been found to be applicable to a large number of data sets. It permits description of an entire exchange isotherm with two parameters obtained directly from measured points on the isotherm. It is shown here that these parameters can be used to derive the true exchange equilibrium constant for the exchange reaction, as well as the exchange‐phase activity coefficients used in thermodynamic approaches based on the Vanselow‐Argersinger (mole fraction) and Gaines‐Thomas (equivalent fraction) conventions. Values of the exchange equilibrium constant and the exchange‐phase activity coefficients calculated from fitted Rothmund‐Kornfeld parameters compare favorably with those calculated using conventional thermodynamic approaches. The method based on the Rothmund‐Kornfeld approach is potentially more accurate because it avoids subjective extrapolation of the data required for the thermodynamic approach.
Influence of Sample Size on Chemical and Physical Soil Measurements
Authors: Starr J. L. , Meisinger J. J. , Parkin T. B. 
Published: July 2010

AbstractUnderstanding the distribution of soil properties with respect to sample size is essential for designing efficient soil sampling strategies. This study was conducted to evaluate the influence of the size of soil samples on the distribution of estimated soil physical (bulk density and water content), chemical (pH and orthophosphate P), and biological (NO3‐N and denitrification rates) properties. The experiment was conducted at Beltsville, MD, on a Beltsville silt loam soil (fine‐loamy, mixed, mesic Typic Fragiudult). Soil samples were collected from the surface layer (0–16 cm) using five different sized soil coring tubes, 1.7 to 5.4 cm in diameter, and one 20 by 30 cm block. Thirty‐six samples of each sample size were collected twice before and twice after planting corn (Zea mays L.). Frequency distributions of denitrification rates, NO3‐N, and orthophosphate P values were approximately lognormal, while the values for bulk density, water content, and pH were approximately Gaussian. All soil parameters except bulk density exhibited spatially dependent results. The effect of sample size varied with the soil property. The most consistent size effect was that smaller diameter samples gave smaller means, greater skewness, and higher variances compared with the large‐block sample statistics.
Straw Application Effects on Methane and Oxygen Exchange and Growth in Rice
Authors: Kludze H. K. , DeLaune R. D. 
Published: July 2010

AbstractCurrently, there is a paucity of information on plant‐soil interactive effects and plant‐related factors that control CH4 production and its emission from rice (Oryza sativa L.) paddies. Laboratory studies were conducted to evaluate the effects of rice straw application rates on growth, root porosity (POR), and gas (O2 and CH4) exchange in rice under continuously flooded conditions. Three rice cultivars were grown in Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf) amended with two levels (11 and 22 t ha−1) of rice straw. Plants were harvested for growth, POR, and radial oxygen loss (ROL) estimates at 40 d after transplanting. Methane measurements were made at 20, 30, and 40 d after transplanting. Plant growth and straw application rates were negatively correlated. Variations existed among cultivars in parameters studied. Although POR was enhanced by the higher application rate (22 t ha−1), reductions in shoot and root growth consequently resulted in reduced ROL. Two of the cultivars exhibited significant POR‐ROL correlations. Highest CH4 emissions occurred at the 11 t ha−1 application rate. At the 22 t ha−1 application rate, CH4 emissions were significantly reduced in all vegetated treatments, although emissions from unvegetated treatments were enhanced. Results indicated that reductions in CH4 emissions at the higher straw application rate resulted from reduction in the total diffusive pathway of the gas and were not due to the mitigation of methanogenesis.
Methyl Bromide Soil Fumigation Alters Plant Element Concentrations
Authors: Ellis J. R. , Varvel G. E. , Watson D. M. H. , Jawson M. D. 
Published: July 2010

AbstractSoil fumigation is used to eliminate plant pathogens and weeds in commercial practice and to eliminate organisms in controlled experiments, e.g., vesicular arbuscular mycorrhizal fungi (VAMF). This study was conducted to study the effect of methyl bromide fumigation on plant accumulation of 14 elements and assess plant colonization by VAMF after fumigation. Field experiments were conducted near Mead, NE, on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll). Corn (Zea mays L.) sorghum [Sorghum bicolor (L.) Moench], and soybean [Glycine max (L.) Merr.] were used in the experiments. Fumigation increased Al, Br, Ca, Fe, Mg, Mn, and Si and decreased Cu, K, P, and Zn shoot concentrations in all three plants. Three weeks after germination, shoot Al was sevenfold greater in sorghum and soybean and 16‐fold greater in corn from fumigated plots than in shoots from nonfumigated plots. Shoot bromide concentrations from fumigated plots were sixfold greater in sorghum and 17‐ to 18‐fold greater in corn and soybean than shoots from nonfumigated plots. Lower P and Zn shoot concentrations from fumigated plots were attributed to fumigation‐induced suppression of VAMF root colonization or an ion balance problem resulting from the enhanced uptake of Al, Br, and other ions after soil fumigation. At harvest, Al was still three‐ to 10‐fold and Br eight‐ to 20‐fold greater in fumigated plot stover compared with nonfumigated plots. This study shows that methyl bromide fumigation alteration of plant uptake of Al, Br, Ca, Fe, Mg, Mn, and Si should be considered when interpreting experiments using methyl bromide soil fumigation.
Improving the Iron Oxide Sink Method for Extracting Soil Phosphorus
Authors: Myers R. G. , Pierzynski G. M. , Thien S. J. 
Published: July 2010

AbstractIron oxide coated filter paper can estimate labile P in soil by acting as a P sink. Variations in procedures and contamination from soil adhering to the sinks limit effective data interpretation, however. We evaluated two papers with pores <5.0 µm and one with pores 20 to 25 µm. Iron oxide coatings were formed by exposing FeCl3‐treated papers to NH3 vapor or 2.7 M NH4OH. Coated papers were either fixed in a screen assembly or allowed to move freely during shaking. The screen assembly eliminated abrasion loss of the FeO coating. Paper circles (5.5 cm) proved satisfactory and eliminated the need to cut 2 by 10 cm strips from coated papers. Fixed, small‐pore circles had less soil contamination (0.8–1.9 mg) than fixed, large‐pore circles (4.7–8.1 mg), a condition confirmed by x‐ray diffraction. Similarly, free, small‐pore circles retained less soil contamination (3.5–9.0 mg) than free, large‐pore circles (16.1–21.7 mg). Two sources of acid‐extractable P inflated the labile P pool. First, acid‐extractable P from soil adhering to papers increased sink‐extractable P by 7.5 to 24.1 mg P kg−1, an error of 28 to 65%. Also, paper prepared in NH3 vapor acidified the extracting solution with Kahola (fine‐silty, mixed, mesic Cumulic Hapludoll) and Haynie (coarse‐silty, mixed [calcareous], mesic Typic Udifluvent) soils and increased their extractable P an average of 13 mg P kg−1, or 56%. To eliminate some analytical problems associated with the FeO‐sink extraction of soil P, we recommend preparing small‐pore circles (<5 µm) in NH4OH solution and securing them during shaking.
Influence of Treethrow on Soil Properties in Northern Wisconsin
Authors: Meyers N. L. , McSweeney K. 
Published: July 2010

AbstractThe uprooting of trees (treethrow) creates major changes in some soil properties. This study was conducted to document both the extent of treethrow activity and its influence on soil properties in northern Wisconsin. We determined the extent of treethrow at 12 localities and studied 10 of those localities in detail. We determined bulk density, particle‐size distribution, P, K, pH, and moisture status of knolls, cradles, and linear areas where recent disturbance was not obvious. The terms knoll and cradle refer to the mound and depression or pit created by treethrow disturbance. We use the term linear area to identify portions of the landscape not identified as knoll or cradle. Knolls have significantly lower bulk densities throughout the upper 90 cm, compared with adjacent cradles and linear areas. Differences in particle‐size distribution are evident to a depth of 90 cm. Potassium contents are significantly higher in cradles than knolls or linear areas. No differences in P levels or pH are evident. Monthly determinations of moisture content during two growing seasons show knolls are drier than cradles or the linear areas. In light of these sizable significant differences, it seems appropriate that disturbance in these landscapes should be identified within map units and considered in both interpretations for use and taxonomic classification.
New Mexican Locust and Parent Material: Influence on Availability of Soil Macronutrients
Authors: Klemmedson James O. 
Published: July 2010

AbstractThe effect of New Mexican locust (Robinia neomexicana Gray) on availability of soil N, P, K, and S in ponderosa pine (Pinus ponderosa Laws.) forests in central Arizona was studied in stands with either basalt or limestone parent material. Samples of the 0‐ to 15‐cm layer of mineral soil were collected from seven pairs (with and without locust) of randomly located stands (sites), three on limestone and four on basalt. Availability of N, P, K, and S in these soils was determined in a greenhouse pot experiment with barley (Hordeum vulgare L. var. gustoe) grown for 42 d. Supply of N and P also was measured in a similar test with ponderosa pine seedlings grown for 270 d. Dry mass yield of test plants was used as the expression of nutrient availability. Barley and pine tests yielded similar results. A significant locust × parent material interaction showed opposite responses to locust presence by soils derived from limestone (positive) and basalt (negative). A highly significant parent material × nutrient interaction reflected low availability of N in limestone soils and low availability of P in basaltic soils. Low supply of P in basaltic soils, probably the result of P fixation, largely explained the locust × parent material interaction.
Sodium/Calcium‐Montmorillonite Suspension and Light Scattering
Authors: Keren R. , Klein Eva 
Published: July 2010

AbstractLight scattering method was used to determine clay concentration in aqueous suspensions. Because light scattering of nonabsorbing solid particles in suspension depends on particle size and shape in addition to the particles' concentration, these two factors should be considered in determination of clay concentration in suspension. this study was conducted to determine the effect of adsorbed ion composition and clay particle size and shape on light scattering of montmorillonite suspensions. Light scattering of montmorillonite suspensions at various particle size, clay concentrations, and equivalent fraction of exchangeable sodium (EFES) was determined at a wavelength of 550 nm. Light scattering of montmorillonite suspensions depended strongly on particle size and EFES. The scattered light intensity decreased as the particle size of the clay platelets decreased and dropped sharply with increasing EFES in the range below 0.2. The relative number of particles in a given volume of suspension at any given EFES value was smaller than predicted by the theory. This deviation indicated that Rayleigh's theory is not valid for such systems. Clay concentration, therefore, cannot be adequately determined by light scattering when changes in ionic composition and electrolyte concentration alter the particle size and shape of montmorillonite in aqueous suspension.
Nitrogen Turnover by Sequential Immobilization and Mineralization during Residue Decomposition in Soils
Authors: Blackmer A. M. , Green C. J. 
Published: July 2010

AbstractAdditions of 15N‐labeled fertilizers to soils often induce mineralization of nonlabeled N, and such mineralization poses problems when interpreting the results of isotopic analyses. We studied the effects of added 15NO−3 on turnover of N during the decomposition of corn (Zea mays L.) residues in soils. Samples of a Galva silty clay loam (fine‐silty, mixed, mesic Typic Hapludoll) were treated with various levels of corn stover and various levels of 15N‐labeled NO−3 and were incubated for 90 d. Evolution of CO2 and concentrations and isotopic composition of NO−3 were monitored. Increases in rates of NO−3 addition increased initial rates of immobilization of labeled N and subsequent rates of mineralization of nonlabeled N. The sequential immobilization of labeled N and mineralization of nonlabeled N resulted in substantial replacement of labeled NO−3 by nonlabeled NO−3. Early added‐N‐induced immobilization of labeled N often was offset by subsequent added‐N‐induced mineralization of nonlabeled N before the end of the study. Sequential immobilization and mineralization should be recognized as a potential source of error in 15N‐tracer studies because sequential processes violate the commonly held assumptions that mineralization and immobilization occur simultaneously. This error could be avoided by recognizing that sequential immobilization and mineralization can occur and that the sequential processes result in a different distribution of isotopes than does simultaneous mineralization‐immobilization turnover.
Metabolism of Carbamothioate Herbicide, EPTC, by Rhodococcus Strain JE1 Isolated from Soil
Authors: Ankumah R. O. , Dick W. A. , McClung G. 
Published: July 2010

AbstractBiodegradation of the her bicide EPTC (s‐ethyl dipropylcarbamothioate) at greatly enhanced rates, which may lead to poor weed control, can occur in soil after successive annual applications. The mechanisms of EPTC degradation by a strain of Rhodococcus sp. (designated JE1) previously isolated from soil were evaluated. Degradation of 14C‐labeled (at the 1‐propyl position) and unlabeled EPTC was followed by thin layer chromatogaphy and gas chromatography‐mass spectrometry. The N‐depropyl EPTC and EPTC sulfoxide were identified as initial metabolites formed, apparently via hydroxylation of the α‐propyl C and oxidation of the S atom of EPTC, respectively. Other products of EPTC degradation identified were propionaldehyde, s‐ethyl carbonothioic acid, s‐methyl carbonothioic acid, and traces of propylamine. It is proposed that the soil isolate Rhodococcus JE1 degrades EPTC via either an initial hydroxylation or sulfoxidation reaction, producing metabolites that can be further mineralized to form CO2. The α‐propyl hydroxylation reaction, however, is thought to be the dominant pathway whereby degradation of EPTC occurs in soil at enhanced rates.
Efficiency of an Incomplete Block Design Based on Geostatistics for Tillage Experiments
Authors: López María V. , Arrúe José L. 
Published: July 2010

AbstractSpatial dependence of soil properties often reduces the power of conventional statistical methods to detect treatment differences. Control of adverse effects of soil variability is of special interest in long‐term experiments when small and slowly developing treatment effects are generally expected to occur, as in tillage research. The main objective of this study was to evaluate the ability of an incomplete block design based on geostatistical concepts to improve the precision of a conservation tillage experiment conducted at four sites in Aragón, northeast Spain. A preliminary geostatistical characterization of plow layer variability at these sites showed that, in most instances, soil water content and silt plus clay content were spatially dependent. Maps of kriged estimates of these properties were used to locate the tillage plots according to the proposed design. Using incomplete blocks of Size 2, the method estimates treatment effects by making short‐distance comparisons and ensures spatially balanced treatment contrasts through fixed comparison distances. This design was compared with a complete block design using soil and crop data obtained during the first two growing seasons of the tillage experiment. The results of a total of 1050 analysis of variance comparisons revealed that the incomplete block design was, on average, 24% more efficient than the complete block design. The use of incomplete blocks reduced the average error mean square by 33% and increased the number of cases with significant tillage treatment differences by 25% compared with the use of complete blocks.
Bioavailability of Citrate‐Insoluble Phosphorus in Monoammonium Phosphate and Triple Superphosphate Fertilizers
Authors: Sikora F. J. , Mullins G. L. 
Published: July 2010

AbstractThe Association of Official Analytical Chemists (AOAC) method for determining bioavailable P was rigorously tested in agronomic studies during the 1930s when the principle constituents of the citrate‐insoluble (CI) fraction were Ca phosphates. The presence of Fe, Al, and Mg phosphate compounds in the CI fraction in today's fertilizers requires a reassessment of the AOAC method. A greenhouse study was conducted to determine if the CI‐P fractions of five monoammonium phosphate (MAP) and five triple superphosphate (TSP) fertilizers were unavailable to sorghum‐sudangrass [Sorghum bicolor (L.) Moench]. Plant shoot weight (SW) and P uptake from fertilizer applied at 15 mg total P kg−1 soil was compared with the same indices obtained from reagent‐grade MAP and monocalcium phosphate (MCP) applied at rates of 13.8, 14.2, 14.6, and 15 mg P kg−1 soil (corresponding to 8, 5.3, 2.7, and 0% reduction in P supply). With a few exceptions, there was good agreement in SW and P uptake among fertilizer and reagent‐grade materials in regard to the percentage of CI‐P in the fertilizer, which lead to the conclusion that the AOAC method correctly determined unavailable P as CI‐P for short‐term plant growth. Residual availability is discussed with reference to the solubility of suspected P‐impurity compounds in the CI fraction.
Reduction of Potassium Fixation by Two Humic Acid Fractions in Vermiculitic Soils
Authors: Olk D. C. , Cassman K. G. 
Published: July 2010

AbstractThe capacity of soil organic matter (SOM) to reduce K fixation was investigated in calcareous vermiculitic soils. Humic acid fractions were extracted with the use of a modification of the standard NaOH extraction procedure. The mobile humic acid pool (MHA) was extracted without initial decalcification. Addition of MHA to the vermiculitic soils reduced K fixation and resulted in greater total extractable K and highly labile K, as well as greater plant K uptake. The Ca humate pool (CaHA) was extracted after decalcification, and it had little effect on K availability. An increase in extractable and highly labile K occurred within 4 h of MHA addition and thus appears to result from a rapid exchange reaction and not from mineral dissolution; the latter was confirmed in separate experiments with organic acids. This rapid effect could be reproduced by addition of dodecylammonium chloride. We speculate that the enriched amino acid content and increased solubility of MHA, compared with the more humified CaHA, contribute to the greater influence of MHA on K equilibria. The less soluble, more condensed CaHA is more likely to precipitate with Ca2+. The capacity of solubilized MHA to hold K+ against soil adsorption was also apparent when soil was separated from MHA by a dialysis membrane. These results provide further evidence that young N‐rich SOM fractions such as MHA play an important role in governing K availability in soils with high K fixation potential.
Short‐Term Effects of Nitrogen Fertilization on Soil Organic Nitrogen Availability
Authors: Vanotti M. B. , Leclerc S. A. , Bundy L. G. 
Published: July 2010

AbstractLong‐term N fertilization affects soil organic N reserves, N mineralization potential, and crop response to applied N, but little information is available on the influence of short‐term N fertilizer (STN) management on soil organic N availability and crop response. This study was conducted to determine if STN changes soil N supplying capability to corn (Zea mays L.) after 3 yr of differential N fertilization on a Fayette silt loam soil (fine‐silty, mixed, mesic Typic Hapludalf) in Wisconsin. Various rates of N fertilizer (0–402 kg N ha−1) were applied to corn in 1983, 1984, and 1985, and their residual effects on corn response were evaluated in 1986. Soil profile No3‐N levels in spring 1986 were very low in all plots (48 ± 4 kg ha−1 [90 cm]−1), yet grain yields and N uptake were significantly increased by STN applications. Corn N uptake was linearly related to the total amount of N returned to soil in crop residues during the previous 3 yr. Increased organic N availability under high STN management was equivalent to a 78 kg N ha−1 rate, or 47% of the N fertilizer required for optimum crop yields. In aerobic incubations (40 wk) of spring 1986 soil (0–30 cm), STN additions increased N release only in the first few weeks. Kinetics of N mineralization were best described by a two‐component model in which the active fraction (NA) of soil organic N was highly correlated with corn N uptake (r = 0.88). Simulation of field conditions showed that 95% of NA is available before crop maturity. A phosphate‐borate buffer organic N availability index was significantly and consistently related to STN treatments. Relative increases in total soil organic N corresponded with the 3‐yr N balance between fertilizer additions and grain removals, and were about 10 times larger than mineralizable N. These results indicate that immobilization of excess mineral N into stable soil organic N during decomposition of crop residues should be considered in determining the environmental risk of N fertilization. Although labile organic N is a small fraction of the total fertilizer N contribution to soil N, its quantification should allow a more accurate assessment of crop N needs.
Pedogenesis of Cotiga Mound, a 2100‐Year‐Old Woodland Mound in Southwest West Virginia
Authors: Cremeens D. L. 
Published: July 2010

AbstractCotiga Mound, an Early Woodland mortuary mound constructed 2100 YBP, was sampled to evaluate diagnostic horizon development during a well‐defined, relatively short period of time. Five columns (profiles), three of which extended into the submound terrace soil, and one Giddings core of the terrace soil were sampled for particle‐size, pH, organic C, and micromorphology analysis. Six additional cores were collected to characterize the terrace soil. The mound was constructed of acid, silty material, in a manner that resulted in basketloading macrofabric consisting of long, sinuous, thin layers contrasting in color and texture. Pedogenesis destroyed the macrofabric and formed a solum in the upper 0.75 to 1.0 m of the mound. The solum consisted of a thin, dark A horizon; and intermittent, thin E horizon; and a variable B horizon. The B horizon was thickest at the mound crest, contained clay films on ped surfaces, and was designated Bt. On side slopes, the B horizon was thinner, lacked clay films, and was designated Bw. No B horizon was formed at the mound periphery. Clay distribution indices indicated that the Bt horizon was borderline cambic‐argillic, consistent with those typical of 2000‐yr‐old mid‐Atlantic alluvial soils. Clay films were sparsely distributed throughout the mound, indicating that clay accumulation mechanisms were largely inefficient in the 2100 yr. Mound soils were classified as Typic Dystrochrepts grading to Typic Hapludults at the mound crest. These soils are similar to floodplain soils mapped nearby. Submound terrace soils and adjacent terrace soils were classified as Humic Hapludults.