bluuebunny/crossref_metadata_2025_split huggingface dataset:
Supercritical Carbon Dioxide Extraction of Long‐Chain Aliphatics from Two Soils
Authors: Schulten H.‐R. , Schnitzer M. 
Published: July 2010

AbstractCurrent trends in soil organic‐matter research are focused on developing methods for the extraction of specific organic‐matter components. One such method is the supercritical gas extraction of soils using CO2. To examine the applicability of this approach to whole soils, we used supercritical CO2 for extracting two soils. The resulting extracts were analyzed by chemical methods, infrared (IR), 13C nuclear magnetic resonance (NMR), and by field‐ionization and field‐desorption mass spectrometry. Major components identified in the extracts were C15 to C41 n‐alkanes, the C8 alkene, the C29 n‐alcohol, C14 to C40 n‐fatty acids, C17 to C41 unsaturated fatty acids, the C18 and C26 dioic acids, the C28 and C30 n‐ketones, C38 to C64 n‐alkyl monoesters, the C52 n‐dioic acid dimer, and the C78 n‐dioic acid trimer. Of special interest was the presence in the extracts of 10‐nonacosanol (C29), a biomarker for coniferous epicuticular waxes. Supercritical CO2 was found to be a mild and specific extractant for the removal of long‐chain aliphatic materials from soils.
Land‐Use Changes Affecting Classification of a Costa Rican Soil
Authors: Wielemaker W. G. , Lansu A. L. E. 
Published: July 2010

AbstractEffects of deforestation and ensuing land use were studied on an Andic Humitropept developed from fluvio‐laharic deposits in the perhumid climatic zone of Costa Rica. Drastic changes in soil climate and land use after deforestation caused compaction and clay mobilization, particularly in the profiles under maize (Zea mays L.) and pasture. The latter process resulted in a change of classification at the order level from Inceptisol to Ultisol.
Neoformation of Palygorskite in a Southern New Mexico Aridisol
Authors: Monger H. C. , Daugherty L. A. 
Published: July 2010

AbstractPalygorskite is the dominant clay mineral in a petrocalcic horizon of the Rotura soil series (a coarse‐loamy, mixed, thermic, Typic Haplargid), a soil of middle Pleistocene age in southern New Mexico. The purpose of this study was to determine if palygorskite is eolian in origin, inherited from its alluvial parent material, or neoformed in the soil. The origin of palygorskite was determined by examining clay mineral distribution, soil‐water extract chemistry, and palygorskite fiber morphology. An eolian origin of palygorskite is unlikely because it is absent in upper soil horizons and no palygorskite was captured in dust traps during a 10‐yr study. An inherited origin is also unlikely because palygorskite is not an inherent component of Rio Grande alluvium. Scanning electron microscopy revealed that delicate palygorskite fibers radiate perpendicularly into pore spaces, which indicates neoformation. The petrocalcic horizon may foster palygorskite neoformation because it is the site of high Mg content and abundant sand‐ and silt‐grain dissolution.
Stable Carbon Isotopic Composition of Carbonate in Holocene Grassland Soils
Authors: Kelly Eugene F. , Amundson Ronald G. , Marino Bruno D. , DeNiro Michael J. 
Published: July 2010

AbstractStable C isotope ratios (13C/12C) and amounts of soil carbonate were measured at six sites of differing temperature, moisture, and vegetational make‐up in the northern Great Plains of the USA in order to determine climatic and biotic influences on the stable C isotope chemistry of these soils. With approximately constant precipitation, total carbonate decreased with increasing temperature. With decreasing precipitation, the total carbonate in the soils increased. For all but one soil, the 13C/12C ratios of segregated carbonate conformed to values expected if the carbonate formed from CO2 derived from soil organic matter. In the nonconforming site, the 13C/12C ratios of the carbonate suggest that the vegetation and soil organic matter have recently become dominated by C4 plants, which use the Hatch‐Slack photosynthetic pathway, and organic matter derived from them. The 13C/12C ratios of disseminated carbonate reflect the proportion of pedogenic and parent‐material carbonate in the sample. The 13C/12C ratios of pure, pedogenic carbonate at each site could be constrained by: (i) measured 13C/12C ratios of soil organic matter, (ii) measured 13C/12C ratios of carbonate nodules, and (iii) calculated 13C/12C ratios using a diffusion model designed by others. Estimates of the percentages of disseminated pedogenic carbonate in the soils suggested that, as the amount of weathering at sites increases and the total carbonate decreases, the percentage of carbonate that remains becomes more dominated by carbonate of pedogenic origin.
Growth Characteristics of Legume Cover Crops in a Semiarid Environment
Authors: Power J. F. 
Published: July 2010

AbstractTo select the best legume cover crop to grow for a given cropping situation, the producer needs knowledge of relative growth rates, N2‐fixation and N‐uptake rates, and water use for various potential planting dates. Such an experiment was conducted for 2 yr at Mandan, ND, in which 10 legume species were planted on or shortly after the first day of May, June, July, and August each year. Soil and plant samples were collected periodically after each planting date to evaluate rates of dry‐matter production, N accumulation, and water use. Potential N2‐fixation rate was measured in one season only. For the first 40 to 90 d after planting, large‐seeded annuals such as faba bean (Vicia faba L.), field pea (Pisum sativum L.), and soybean (Glycine max [L] Merr.) generally exhibited most rapid growth, N accumulation, and water use (these three parameters were generally closely related for all samplings). With more than 90 d growth, species such as Korean lespedeza (Lespedeza stipulacea Maxim.), yellow sweet clover (Melilotus officianalis L.), and alfalfa (Medicago sativa L.) also began to exhibit rapid growth. One surprising result was the outstanding growth of May‐planted subterranean clover (Trifolium subterraneum L.) in one (ample moisture) of the two seasons. For the shorter growth periods, faba bean exhibited good growth characteristics at all planting dates, and field pea was satisfactory at most. July and August planting of slower growing species generally resulted in relatively little growth by the end of the season. In most instances, water‐use efficiency was greatest for the May planting, and highest values were often recorded for field pea, faba bean, and subterranean clover. These results identify those legume species best adapted for a given planting date and duration of growth under the climatic conditions of this experiment.
Motor‐Driven Portable Soil Core Sampler for Volumetric Sampling
Authors: Hendrickx J. M. H. , Ritsema C. J. , Boersma O. H. , Dekker L. W. , Hamminga W. , van der Kolk J. W. H. 
Published: July 2010

AbstractAn improved soil core sampler was tested for measuring bulk densities and volumetric water contents of field soils. The improvements consist of (i) a portable gasoline‐driven mechanical hammer and (ii) a wide cut‐out trough with removable cover. The improved hammer uses high‐frequency vibrations to drive the core sampler into the soil at an even speed without interruption, thus preventing compaction. The new trough allows free access for sampling the soil core with 205‐cm3 steel cylinders. Samples were taken by the improved soil core sampler and by hand in sand, silt loam, and clayey peat soils. Comparison of these samples showed that the improved soil core sampler provides volumetric soil samples that are sufficiently accurate in bulk density and volumetric water content as those taken manually.
Spectroscopic Study of Surface Redox Reactions with Manganese Oxides
Authors: Risser Jeffrey A. , Bailey George W. 
Published: July 2010

AbstractRedox reactions involving soil minerals and materials are important processes in environmental chemistry, but unfortunately they only have been characterized in the solution phase. The lack of a suitable method has prevented investigations of the mineral surface component of redox reactions. We present a model system in which ultraviolet‐visible spectroscopy is employed to observe a surface redox reaction. A synthetic MnOx is reacted with Cr(III), resulting in Cr oxidation to the hexavalent state and the reduction of the MnOx mineral. A scattered transmission accessory allowed us to observe spectroscopically both the appearance of Cr(VI) and the attenuation of MnOx in a suspension. Loss of absorbance intensity by MnOx suspensions may be useful as a general method to follow redox reactions as a function of the solid phase rather than relative to a specific reactant. This spectroscopic approach provides the capability to monitor in situ reactions of solid‐phase components and is useful for examining transformations of metallic and organic wastes and naturally occurring materials in the environment.
Sources of Nitric Oxide and Nitrous Oxide following Wetting of Dry Soil
Authors: Davidson Eric A. 
Published: July 2010

AbstractWhen dry soil is wetted, significant fluxes of NO and N2O have been reported. The sources of these gases have been difficult to identify because a number of biological and abiological processes can produce both gases. Soil sampled from an annual grassland in central California at the end of the dry season was wetted to soil water contents above and below field capacity. Production of NO and N2O began within minutes of adding water. Below field capacity, the net production of NO exceeded N2O, whereas above field capacity the production of N2O exceeded NO. Production of NO was inhibited by acetylene (C2H2) at both water contents, indicating that the NO source was dependent on nitrification. In contrast, N2O production was inhibited by C2H2 only when soil water was below field capacity, indicating that denitrification was the dominant source when soil water was above field capacity. Addition of NO‐2 also stimulated NO production in both sterile and nonsterile soil, suggesting that abiological reactions could contribute significantly to NO emissions. Production of NO‐2 and H+ by NH+4‐oxidizing bacteria, followed by chemodenitrification of a small fraction of the NO‐2 produced, could account for the observed NO fluxes from dry and moist soil. Nitrifying and denitrifying bacteria appear to be well adapted to surviving extreme drought and to becoming active with minutes of wetting dry soil.
Early Cropping‐Induced Changes in Soil Aggregation, Organic Matter, and Microbial Biomass
Authors: Angers D. A. , Pesant A. , Vigneux J. 
Published: July 2010

AbstractCrop management practices influence the amount and quality of organic matter and the state of aggregation in soils. The objective of this study was to determine the early changes in organic and microbial‐biomass C contents and in water‐stable aggregates of two loamy soils (Typic Fragiaquept and Typic Haplaquept) following plowing of a meadow and subsequent planting of either corn (Zea mays L.) or barley (Hordeum vulgare L.). The effects of 1, 2, and 3 yr of cropping with these two crops were compared with an undisturbed and a recently plowed meadow. Plowing decreased the organic and microbial‐biomass C contents of the surface soil (0–6 cm) by an average of 40 to 50%, but, when the whole surface horizon (0–24 cm) was considered, there was no effect. Further cropping with either corn or barley resulted in no net loss of organic matter and microbial biomass but only a redistribution in the surface soil profile. Microbial‐biomass C was not preferentially affected by cropping relative to total organic C. The mean‐weight diameter of water‐stable aggregates decreased not only with plowing but also with length of cropping both in the surface soil (0–6 cm) and throughout the top 24 cm. There was little difference in the specific effects of the two crops on organic C, microbial‐biomass C, or aggregation.
Effect of Diffusion and Sorption on the Kinetics of Biodegradation: Theoretical Considerations
Authors: Scow Kate M. , Hutson John 
Published: July 2010

AbstractOrganic chemicals subject to biodegradation by microorganisms in soil are often limited in their availability by sorption and diffusion to unavailable sites. To quantitatively describe biodegradation under conditions of substrate limitation, a process‐based deterministic model called the diffusion‐sorption‐biodegradation (DSB) model was developed to describe the biodegradation of an organic chemical in the presence of spherical aggregates. Diffusion is described by Fick's second law, sorption by a linear isotherm, and biodegradation by one of various rate equations including first‐order kinetics. Sensitivity analyses were performed to determine the dependence of a chemical's half‐life on soil physical and chemical properties. Half‐lives in the presence of aggregates were substantially greater than equivalent half‐lives in the absence of aggregates when the sorption partition coefficient was ≥3.2 dm3kg‐1 and the aggregate radius was ≥0.32 cm. The two‐compartment model provided a better fit than did a simple first‐order model to simulations of the biodegradation of a sorbing chemical in the presence of large (0.25‐cm radii) aggregates, whereas there was no difference between the two models for aggregates of much smaller radii. When simple first‐order kinetics was assumed without accounting for diffusion and sorption, long‐term extrapolation of chemical persistence in the presence of aggregates overestimated the degradation of a chemical with a sorption partition coefficient of 10 dm3kg‐1. Considering that many organic pollutants sorb strongly and numerous soils have some degree of aggregate structure and organic matter, taking into account the physical and chemical processes affecting a chemical's concentration may greatly improve kinetics models of biodegradation in soil.
Effect of Diffusion on the Kinetics of Biodegradation: Experimental Results with Synthetic Aggregates
Authors: Scow Kate M. , Alexander Martin 
Published: July 2010

AbstractThe rates of biodegradation in soil often do not conform to the predictions of kinetic models, such as the first‐order and Michaelis‐Menten models, developed to describe metabolic processes occurring in solutions in which microorganisms and their substrates are well mixed. To test whether the kinetics of biodegradation in the presence of aggregates could be described by explicitly accounting for chemical diffusion, studies were conducted in well‐defined experimental systems. The kinetics of biodegradation of low concentrations of 14C‐labeled phenol and glutamate by Pseudomonas sp. Strain K in buffer containing spherical aggregates of kaolinite that exclude bacteria were significantly different from the kinetics measured in the absence of aggregates. Both the biodegradation rate and the percentage of the initial compound degraded were lower in the presence of aggregates than in their absence. Using measurements of biodegradation, diffusion rates, and physical properties of the experimental system as input parameters, the diffusion‐sorption‐biodegradation (DSB) model simulated the biodegradation of phenol and glutamate originating inside aggregates. The model also simulated the initial period of biodegradation of glutamate in an experimental system containing gel‐exclusion chromatography beads. Clay aggregates reduced the concentration of available p‐nitrophenol sufficiently to lower the apparent rate constant for its biodegradation. Microscopic mass‐transfer processes, such as diffusion, may be important to consider in quantitative descriptions of the biodegradation of organic chemicals in soil.
Liming Double‐Cropped Ryegrass and Sorghum
Authors: Morris D. R. , Joost R. E. , Corkern D. L. , Mason L. F. 
Published: July 2010

AbstractThe grower must apply lime to maintain crop yields when double‐cropping forage sorghum [Sorghum bicolor (L.) Moench] in summer and ryegrass (Lolium multiflorun Lam.) in winter on Coastal Plain soils of the U.S. Southeast. The purpose of this research was to determine the frequency and rate of liming needed for optimal growth of these crops and to identify soil properties having greatest effect on yield. The experiment was conducted on a Tangi silt loam (fine‐silty, siliceous, thermic Typic Fragiudult) during a 12‐y period. Dolomitic lime treatments were: 0 lime, 2.2 and 4.4 Mg lime ha‐1 applied every 2yr, and 2.2 and 4.4 Mg lime ha‐1 applied every 4 yr. Soil samples were taken annually and analyzed for pH, exchangeable Al, Ca, Mg, and K, and extractable P. Surface soil pH was maintained at 5.8 and 6.0 when lime was applied at 2.2 and 4.4 Mg ha‐1 every 2 yr. Soil pH declined when lime was applied every 4 yr. In unlimed soil, the pH declined from 5.6 to 4.7 during the 12 yr. Significant differences in forage yields between unlimed and limed treatments did not occur until the sixth year (for sorghum) and the 11th year (for ryegrass). Reduced yields of ryegrass first occurred when soil pH decreased to 4.8 ± 0.11; for sorghum, yields declined at pH 5.2 ± 0.078. Crop yields of limed treatments were not affected by liming frequency. It may take longer than 12 yr for soil property differences among lime treatments to be large enough to alter plant yields. Ryegrass yield was not correlated with any surface soil parameters; Sorghum yield was positively correlated with surface soil extractable Ca. Exchangeable Al tended to decline and extractable Ca and Mg tended to increase with lime applications. Neither extractable P nor K was signigicantly altered by lime treatment. In a double‐cropped system of ryegrass and sorghum, liming would be of more benefit to sorghum.
Nitrous Oxide Emissions in Irrigated Corn as Affected by Nitrification Inhibitors
Authors: Bronson K. F. , Mosier A. R. , Bishnoi S. R. 
Published: July 2010

AbstractNitrous oxide and N2 are the major denitrification products in irrigated corn (Zea mays L.). In addition, N2O is considered a gas that contributes to global warming and stratospheric O3 depletion. Minimizing N2O emissions in cropping systems is therefore an economic as well as an important environmental concern. In a 1989 field experiment, the nitrification inhibitor encapsulated calcium carbide (ECC) (0, 20, or 40 kg CaC2 ha‐1) or nitrapyrin (0.5 L a.i. ha‐1) was banded with urea (218 kg N ha‐1) 7 wk after planting corn. Between 1 and 14 wk after fertilization in 1989, N2O losses of 3226, 1109, 1017, and 1005 g N2O‐N ha‐1 from urea alone, urea plus nitrapyrin, urea plus 20 kg ECC ha‐1, and urea plus 40 kg ECC ha‐1, respectively, were measured from vented chambers. Nitrous oxide fluxes were positively correlated with soil NO3 levels, indicating that the nitrification inhibitors indirectly controlled N2O emissions by preventing NO3 from accumulating in the soil. Carbon dioxide emissions from the root zone were generally not affected by ECC or nitrapyrin. In 1990, losses of N2O were less than in 1989 (1651 g N ha‐1 with urea alone), probably because there were fewer irrigations. Nitrapyrin and ECC addition to urea resulted in 980 and 459 g N ha‐1 N2O being emitted the second year. Nitrification inhibitors appear to be a useful tool in mitigating N2O emissions in agricultural systems.
Interrill Erodibility of Some Ohio Soils Based on Field Rainfall Simulation
Authors: Bajracharya R. M. , Elliot W. J. , Lal R. 
Published: July 2010

AbstractPrediction of soil erodibility and an understanding of erosion processes are vital to sustained productive use of agricultural land. Interrill erodibilities (Ki) of five Ohio soils were assessed and compared with predicted Ki using the Water Erosion Prediction Project equation (WEPP‐K). A portable rainfall simulator was used to apply ∼ 70 mm h‐1 intensity rain for 1 h on 0.75‐m2 field plots representing crop row sideslopes. The soils studied included Miamian (fine, mixed, mesic Typic Hapludalf) and Riddles (fine‐loamy, mixed, mesic Typic Hapludalf) silt loams, Crosby silt loam (fine, mixed, mesic Aeric Ochraqualf), Kokomo silty‐clay loam (fine, mixed, mesic Typic Argiaquoll) and Mechanicsburg loam (fine‐loamy, mixed, mesic Ultic Hapludalf). The value of Ki determined for each soil was related to selected physical and chemical properties. Values of Ki varied significantly between soils and ranged from 1.23 ± 0.09 to 1.97 ± 0.60 × 10‐6 kg s m‐4. Interrill erodibility was negatively correlated with water‐stable aggregates (WSA) >0.25 mm (r2 = 0.50), WSA > 0.5 mm (r = 0.49), and organic C (r2 = 0.61), and positively correlated with Middleton's dispersion ratio (r2 = 0.84) and the ratio of water‐dispersible clay to total clay (r2 = 0.70). The WEPP‐Ki differed from measured values by ∼ 10 to 40%, ranging from 1.1 to 2.0 kg s m‐4. There was no correlation between WEPP‐Ki and measured Ki.
Isotopic Composition of Hydration Water in Gypsum and Hydroxyl in Jarosite
Authors: Dowuona G. N. , Mermut A. R. , Krouse H. R. 
Published: July 2010

AbstractData on the isotopic composition of hydration water in gypsum and hydroxyl in jarosite are rare. This study was initiated to measure the δ18O and δD (deuterium) values of hydration water in gypsum and hydroxyl in jarosite and to determine their relationship with the isotopic composition of environmental water. Gypsum and jarosite in soils from different localities in Saskatchewan, Canada, were sampled for O and H isotope analyses. Two samples from Maryland and one from Thailand were included for comparison. The δD and δ18O values of hydration water in gypsum and hydroxyl in jarosite varied from ‐166 to ‐80‰ and ‐17 to ‐9‰, respectively. Gypsum and jarosite samples from Saskatchewan generally followed the gradient in isotopic composition of local precipitation with slopes of 8.9 and 8.6, respectively. Samples from Maryland and Thailand, which are located at lower latitudes, showed relative enrichment in D and 18O, compared with the samples from Saskatchewan. The δD and δ18O data of samples from Saskatchewan, Maryland, and Thailand plot along a straight line with a steep slope of 11.5 due to the relative D and 18O enrichment in samples from Maryland and Thailand. Because the isotopic composition of hydration water of gypsum and hydroxyl of jarosite reflect that of water in the soil environment, they may be useful as a proxy for the isotopic composition of soil moisture at depths where gypsum or jarosite precipitates.
Pool Size and Mean Age of Stable Soil Organic Carbon in Cropland
Authors: Hsieh Yuch‐Ping 
Published: July 2010

AbstractMost modern surface soils are believed to contain a pool of very stable soil organic carbon (SOC) with a mean age (MA) that may reach several thousand years. The remaining SOC pools are much younger, perhaps no older than a few decades. The SOC can thus be divided into two major classes: very old (stable pool) and relatively young (active pool). Because active and stable SOC play very different roles in soil organic‐matter dynamics and nutrient cycling, it is desirable to know the pool size and turnover time of the two fractions in an ecosystem. Unfortunately, none of the physical or chemical fractionation methods can satisfactorily separate active from stable SOC. The pool size and MA of the stable SOC pool in the surface soil of the Morrow Plots (University of Illinois) and Sanborn Field (University of Missouri) were determined using the concept of management‐induced differential decomposition of active SOC in a pair of soil samples and the principle of radiocarbon dating. Pool size and MA of the stable SOC in the surface soil (0–20 cm) was estimated at 11.0 g/kg and 2973 yr for the Morrow Plots and 7.3 g/kg and 853 yr for Sanborn Field, respectively.