bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soil Pattern Recognition with Fuzzy‐c‐means: Application to Classification and Soil‐Landform Interrelationships
Authors: Odeh I. O. A. , McBratney A. B. , Chittleborough D. J. 
Published: July 2010

AbstractSoil variation is more continuous than discrete and therefore calls for a continuous approach to soil classification. Fuzzy set theory provides such an approach that quantitatively assigns individuals to geographically and taxonomically continuous classes. We hypothesized that the fuzzy‐c‐means algorithm, based on a fuzzy objective function, could be used to quantify pedons into intragrade and extragrade classes and that minimization of the function would allow for the most “precise” classification, which could be validated by mathematically heuristic methods. These methods assume that local extreme (or abrupt changes) in the value of the objective function or its derivatives indicate optimal grouping. This approach was applied on two transects traversing a subcatchment in the central Mount Lofty Ranges, South Australia. The resulting fuzzy soil classes were found to have reasonable spatial continuity and contiguity, which were associated with local variation in slope features and parent material. Thus the approach identified plausible groupings (substructures) among the soil individuals that realistically reflected changes in the external factors (principally landform and lithology) controlling the processes generating the substructures. The structure‐factor relationships could be used for further rapid soil pattern recognition embodied in soil classification and mapping.
Biodegradability of Dissolved Organic Matter in Forest Throughfall, Soil Solution, and Stream Water
Authors: Qualls Robert G. , Haines Bruce L. 
Published: July 2010

AbstractHigh concentrations of dissolved organic matter (DOM) were leached into rainwater passing through the canopy and forest floor of an oak (Quercus spp.)‐hickory (Carya spp.) forest in the southern Appalachian Mountains. More than 95% of this dissolved organic C (DOC) and N (DON) was removed as water percolated through the soil profile and left the ecosystem in stream water. Our objective was to examine the importance of decomposition in the removal of DOC and DON. Samples of DOM from throughfall, forest floor water, soil water from A and B soil horizons, and stream water were all adjusted to a common initial DOC concentration, inoculated with soil and stream microbes, and incubated in solution for 134 d. In general, only 14 to 33% of the DOC in forest floor, soil solution, and stream samples decomposed during the incubation. The relative order of average decomposition of DOC from the various strata was, from fastest to slowest; throughfall, Oi horizon (forest floor), Oa horizon (forest floor), B horizon, stream, AB horizon, isolated fulvic acid, and upper A horizon. In short, biodegradability of DOM in the ecosystem profile declined vertically from throughfall to the A horizon and then increased with depth. The DON generally did not decay faster than the DOC — results consistent with the idea that hydrolysis of organic N is linked to mineralization of DOC rather than occurring selectively in response to the biochemical need for N. Throughfall DOM could be decomposed during its passage through the upper soil, but decomposition seems too slow to be responsible for the bulk of removal of DON and DOC that occurs in the mineral soil. Adsorption, rather than biodegradation, is more likely responsible for maintaining low DOC substrate concentrations in the mineral soil and preventing its loss into stream water.
Identification of Nutritional Influences on Cone Production in Fraser Fir
Authors: Arnold Roger J. , Jett J. B. , Allen H. L. 
Published: July 2010

AbstractFraser fir [Abies fraseri (Pursh) Poir.] is highly valued as a freshcut Christmas tree. Commercial cultivation is limited partly by seed scarcity. The purpose of this study was to develop foliar tissue nutrient norms for female cone yield to use in the Diagnosis and Recommendation Integrated System (DRIS), for ultimately improving cone yields. Two sets of these norms were developed, one set based on February and the other on July foliar nutrient levels. Neither single mineralnutrient concentrations nor other assessed tree parameters correlated with cone yield. However, nutritional discrimination between high‐and low‐yielding trees was obtained with July tissue. Discrimination with February needle samples was poor. Reasonable agreement was obtained for orders of nutrient limitations diagnosed from the two seasonally specific sets of norms. Results indicated the potential to use DRIS to aid in selection of clones and prescribing treatments to enhance cone yields.
Ridge‐Tillage Corn Response to Point‐Injected Nitrogen Fertilizer
Authors: Blaylock A. D. , Cruse R. M. 
Published: July 2010

AbstractManagement practices to improve N‐use efficiency have been studied repeatedly for conventional tillage and no‐till systems. Little work has been done, though, to identify efficient N‐placement methods for ridge‐tillage systems. The objective of this study was to test the hypothesis that point injection of N in the ridge can optimize N‐use efficiency and corn (Zea mays L.) production in ridge tillage, compared with broadcast N or injection between rows. Corn‐soybean [Glycine max (L.) Merr.] rotation studies were conducted between 1986 and 1988 on Webster and Marna silty clay loams (fine‐loamy, mixed, mesic Typic Haplaquoll and fine, montmorillonitic, mesic Typic Haplaquoll, respectively). Treatments consisted of a control (no N) and factorial combinations of three N‐placement methods (broadcast, point injection between rows, or point injection in rows) and five rates (22, 45, 67, 112, and 157 kg N ha−1) applied as urea‐NH4NO3 solution (UAN). Fertilizer‐N recovery by plants was determined at four growth stages in labeled‐N microplots. Corn yields, percentage of N derived from fertilizer, and percentage of fertilizer N recovered were significantly greater with injected N than with broadcast N. Injection position generally did not affect plant response. Point injection of N fertilizer can improve N‐uptake efficiency over broadcast methods in ridge‐tillage corn, but the importance of injection position was not substantiated.
Bypass Water Flow through Unsaturated Microaggregated Tropical Soils
Authors: Radulovich R. , Sollins P. , Baveye P. , Solórzano E. 
Published: July 2010

AbstractRecent evidence suggests that bypass flow occurs in many soils even under unsaturated conditions, but experimental confirmation is lacking. We measured bypass flow in two microaggregated Inceptisols from the humid Atlantic region of Costa Rica under water‐application rates below those needed to produce ponding. Water was applied with a constant‐head rainfall simulator to undisturbed soil cores taken when soils were near field capacity. Mass of soil core and of water exiting the core (outflow) and time to first appearance of water at the bottom of the core (breakthrough) were recorded. For each application rate, steady‐state outflow was reached quickly at a core mass well below that corresponding to soil saturation. (In contrast, classical theory for sandy soils without macropores, based on the Richards' equation, predicts that breakthrough should take more than twice the time actually observed.) Successive step increases in application rate produced successively smaller increases in core mass and decreases in the lag time before outflow increased. Our results suggest that bypass flow will occur in the noncapillary interpedal pore space whenever the application rate exceeds the infiltration rate of individual microaggregates. Because values for matrix conductivity are extremely low (much less than typical rainfall rates), we suggest that bypass flow may be the rule rather than the exception in microaggregated soils with extensive interpedal noncapillary pore space.
Partitioning Dissolved Inorganic and Organic Phosphorus Using Acidified Molybdate and Isobutanol
Authors: Jayachandran K. , Schwab A. P. , Hetrick B. A. D. 
Published: July 2010

AbstractQuantification of P‐mineralization rate in soil using isotopic dilution requires that soluble inorganic 32P (32Pi) be determined without interference from soluble organic 32P (32Po). Therefore, a method is needed to partition 32Pi and 32Po into physically separate solutions before radiation counting. A previously suggested method of extracting Pi into isobutanol with acidified molybdate was tested for efficiency of separation from Po. Inorganic P as KH2PO4 was completely recovered in the isobutanol phase with acid molybdate. Organic P (glycerophosphate) remained in the aqueous phase during the extraction. No Po hydrolysis was observed when sodium phytate, glycerophosphate, ribonucleic acid, adenosine 2′‐ and 3′‐monophosphate, and cytidine 2′‐ and 3′‐monophosphate were extracted, but detectable amounts of adenosine 5′‐triphosphate hydrolyzed. This technique was tested on four Kansas soils, and the levels of inorganic and organic P obtained by this method were the same as those detected by conventional analyses.
Nitric Oxide and Nitrous Oxide Production from Soil: Water and Oxygen Effects
Authors: Drury C. F. , Findlay W. I. , McKenney D. J. 
Published: July 2010

AbstractThis study was designed to determine the effects of water and O2 on the speciation of denitrification gases (NO and N2O). Nitric oxide was found to be the principal end product from soil incubated under low‐moisture conditions, whereas the relative amount of N2O increased under wetter moisture regimes. The total amount of NO plus N2O produced increased with increasing water content for the Brookston clay loam (fine‐loamy, mixed, mesic Typic Argiaguoll), whereas it peaked at 150 g kg−1 (15%) water content with the Fox sandy loam (fine‐loamy over sandy or sandy or sandy‐skeletal, mixed, mesic, Typic Hapludalf). The decrease in NO plus N2O at higher water contents was probably the result of the subsequent reduction of N2O to N2 in the Fox sandy loam soil. The residence time of the denitrification gases in the soil increased with increasing water content, hence facilitating the subsequent conversions of NO to N2O and N2. The thickness of the water film surrounding the microbes affected both the diffusion of O2 through the water and into the microbes as well as the diffusion of denitrification gases (NO, N2O, and N2) from the microbes into the atmosphere. In the sandy loam soil, O2 content and soil water affected both the amount and species of evolved denitrification gases. Oxygen was more effective in decreasing NO production at lower than at higher water contents.
Phosphorus Distribution in Loessial Fragiudalfs as Affected by Relief
Authors: Switzer R. E. , Pettry D. E. 
Published: July 2010

AbstractTopographic effects on P form and distribution were determined in three loessial toposequences. Loring soils (fine‐silty, mixed, thermic Typic Fragiudalfs) were sampled in the top‐ and midslope positions. Slopes ranged from 1 to 2% in the topslope and 9.5 to 13% in the midslope pedons. Phosphorus distribution reflected changes in topographic position and the influence of fragipan horizons (Btx) in the pedons. Nonoccluded, occluded, organic, and total P decreased while Ca‐P increased as slope increased. Nonoccluded exceeded occluded P in the topslope Bt horizons, while occluded P dominated in the Btx horizons. Occluded P dominated midslope Bt and Btx horizons. Results suggest a loss of P and a reduction in weathering intensity as slope increased. Significant correlations were found between nonoccluded and occluded P and clay, dithionite‐ and oxalate‐extractable Fe, and total Fe while Ca‐P and organic P were correlated with pH and base saturation in the topslope pedons. In the midslope pedons, significant correlations were found between occluded P and clay and dithionite‐extractable Fe while Ca‐P and organic P were correlated with pH, base saturation, and organic matter. Maximum clay and total P occurred in similar Bt horizons in all topslope pedons. Changes in P distribution occurred into and below the Btx horizons, suggesting these changes occurred prior to and during fragipan formation.
High Dimensional Reflectance Analysis of Soil Organic Matter
Authors: Henderson T. L. , Baumgardner M. F. , Franzmeier D. P. , Stott D. E. , Coster D. C. 
Published: July 2010

AbstractRecent breakthroughs in remote‐sensing technology have led to the development of high spectral resolution imaging sensors for observation of earth surface features. This research was conducted to evaluate the effects of organic matter content and composition on narrow‐band soil reflectance across the visible and reflective infrared spectral ranges. Organic matter from four Indiana agricultural soils, ranging in organic C content from 0.99 to 1.72%, was extracted, fractionated, and purified. Six components of each soil were isolated and prepared for spectral analysis. Reflectance was measured in 210 narrow (10‐nm) bands in the 400‐ to 2500‐nm wavelength range. Statistical analysis of reflectance values indicated the potential of high dimensional reflectance data in specific visible, near‐infrared, and middle‐infrared bands to provide information about soil organic C content, but not organic matter composition. Although reflectance in the visible bands (425–695 nm) had the highest correlation (r = −0.991 or better) with organic C content among the soils having the same parent material, these bands also responded significantly to Fe‐ and Mn‐oxide content. For soils formed on different parent materials, five long, middle‐infrared bands (1955–1965, 2215, 2265, 2285–2295, and 2315–2495 nm) gave the best correlation (r = −0.964 or better) with organic C content. Several wavebands were identified in which the soils were separable, but the reflectance response was dominated by soil factors other than organic matter content, indicating that choice of wavebands should not be based on spectral curve separability alone.
Infiltration Rate of a Sandy Loam Soil: Effects of Traffic, Tillage, and Plant Roots
Authors: Meek B. D. , Rechel E. R. , Carter L. M. , DeTar W. R. , Urie A. L. 
Published: July 2010

AbstractSettling and trafficking of a soil after tillage causes rapid changes in the soil physical condition until a new equilibrium is reached. In the soil studied, a Wasco (coarse‐loamy, mixed, nonacid, thermic Typic Torriorthent) sandy loam, soil compaction reduces infiltration rates, which under grower conditions could result in inadequate infiltration of irrigation water to supply crop requirements. Our objective was to evaluate important management practices as they relate to changes in the infiltration rate of a sandy loam soil. Factors evaluated were traffic, tillage between crops, and the formation of channels by roots of perennial crops. Tillage between crops increased the infiltration rate during the first part of the season in trafficked soils but decreased or had no effect on nontrafficked soil. Alfalfa (Medicago sativa L.) increased the infiltration rate fourfold during a 2‐yr period in a heavily compacted soil. An increase in bulk density from 1.6 to 1.8 Mg m−3 decreased infiltration rate 54% in the field. Hydraulic conductivity of undisturbed cores was at least seven times larger than that measured in columns of disturbed soil (same bulk density). This difference is believed to be the result of natural channels in the undisturbed soil that are destroyed when the soil is disturbed. Under controlled traffic, when surface seal is not a problem, tillage will not be necessary to obtain adequate infiltration rates except in the wheel paths.
Nitrogen and Phosphorus Release from Decomposing Needles of Southern Pine Plantations
Authors: Polglase P. J. , Jokela E. J. , Comerford N. B. 
Published: July 2010

AbstractFertilizer application and weed‐control treatments have increased biomass accumulation of loblolly (Pinus taeda L.) and slash pines (P. elliottii Engelm. var. elliottii) in north‐central Florida. While the effects of these treatments have been immediate, the long‐term influences on rates of nutrient cycling are unknown. This study measured rates of mass loss and changes in N and P contents in Oi horizon needles decomposing in the laboratory, and in Oi, Oe1, and Oe2 horizon needles decomposing in situ (litterbag study). The quality of organic‐matter substrates in needles (determined by laboratory incubation) was increased by both weed‐control and fertilizer treatments (P < 0.05), and litter quality of loblolly pine was greater than that of slash pine. However, these effects were not manifest in the field study. Across all treatments, an average of 31% of the original organic matter was lost after 1 yr of decomposition in situ. Generally, N was immobilized into Oi horizon needles but was released in modest amounts (<15% yr−1) from Oe1 and Oe2 horizon needles. In contrast, substantial release of P from Oi horizon needles (>35% yr−1) was followed by smaller release from Oe1 and Oe2 horizon needles (< 15% yr−1). More P was cycled per unit of organic matter in fertilized than nonfertilized plots, and loblolly pine cycled more P than slash pine. Changes in total P content of needles during decomposition were accounted for by changes in the pool of inorganic P. The rapid recycling of P in fertilized plots has the potential to enhance long‐term productivity beyond the immediately beneficial effects derived from fertilizer uptake.
Thiosulfate Inhibition of Urea Hydrolysis in Soils: Tetrathionate as a Urease Inhibitor
Authors: Sullivan D. M. , Havlin J. L. 
Published: July 2010

AbstractAmmonium thiosulfate [ATS, (NH4)2S2O3, 12‐0‐0‐26S] added to urea‐ammonium nitrate (UAN) inhibits urea hydrolysis after application to soil. Thiosulfate itself does not inhibit purified jackbean urease, so products of S2O2‐3 oxidation in soil (tetrathionate [S4O2‐6], Fe2+, and Mn2+) are the probable urease inhibitor(s). The objectives of this study were to (i) identify the primary urease inhibitor produced by ATS in soil and (ii) determine why the efficacy of the inhibitor is improved by increasing UAN droplet size. Jackbean urease (urea amidohydrolase, Type III from jackbean, EC 3.5 1.5) was inhibited by Fe2+ (100% inhibition at 0.3 mM), Mn2+ (100% at 6.3 mM), Fe3+ (97% at 6.3 mM), and S4O2‐6 (39% at 7.8 mM). Thiosulfate did not inhibit jackbean urease at concentrations up to 18.8 mM. When applied in a simulated UAN fertilizer band, S4O2‐6 was as effective as S2O2‐3; it inhibited soil urease (24%) to the same extent as S2O2‐3 (26%) but more than FeSO4 (0%) in two soils. Urease inhibition by all species was low in unbuffered 5‐h soil incubations (Fe2+ [14%], Mn2+ [3%], S4O2‐6 [10%], and S2O3 [7%]) with 25 mmol S kg−1. Urease inhibition by S4O2‐6 increased from 9% at pH 7 to 30% at pH 8.5 in buffered incubations. Since pH during urea hydrolysis increases with UAN droplet size, the increased efficacy of ATS with application of large UAN droplets is probably due to greater activity of S4O2‐6 as a urease inhibitor at pH > 7. Tetrathionate is the primary urease inhibitor produced by ATS in soil. Reaction of urease sulfhydryl groups with S4O2‐6 is proposed as an inhibitory mode of action.
Association of Microcrystalline Goethite and Humic Acid in Some Oxisols from Brazil
Authors: Fontes M. R. , Weed S. B. , Bowen L. H. 
Published: July 2010

AbstractOxisols from the cocoa‐growing region of the state of Bahia, Brazil, may contain large amounts of Fe oxides and significant amounts of organic C to depths exceeding 2 m. The nature of the association of organic C and crystalline oxides was the objective of this study. Alkali extracts (0.1 M NaOH) of soil material taken from different depths in three Typic Hapludox and one Humic Hapludox were characterized by chemical analysis, x‐ray diffraction, Mössbauer spectroscopy, electron microscopy, surface area determination (N2 adsorption), Fourier‐transform infrared spectroscopy, and phosphate adsorption. Microcrystalline goethite was the only inorganic phase accompanying the humic acid in the alkaline solution and humic acid was essential for goethite to be extracted. Mössbauer spectra confirmed the absence of Fe oxides other than goethite in the humic‐acid extracts although hematite and ilmenite were identified in the total soil material. The goethite particles were 10 to 15 nm in diameter and nearly equidimensional. Infrared spectra of the humic acid‐goethite complex indicated that the COOH group was in the salt form, suggesting bonding through this group to the goethite surface. Phosphate adsorption was markedly higher on the humic‐acid‐free goethite than on the complex, indicating competition for adsorption on the goethite by the humic acid. Apparently, the interaction between the humic acid and the goethite involves iigand exchange in addition to coulombic attraction, and may significantly modify the properties of the Fe oxide.
Soil Gas Permeability as Influenced by Soil Gas‐Filled Porosity
Authors: McCarthy Kevin P. , Brown Kirk W. 
Published: July 2010

AbstractThe need to characterize the fundamental gas flow properties of soils has taken on new significance in recent years with the advent of induced soil venting as a remediation technique for contaminated soils. The purpose of this study was to characterize the relationship between soil gas permeability and soil gas‐filled porosity, and the effect of various soil physical properties on this relationship. A gas permeameter was developed to study gas flow through undisturbed soil cores from two horizons in each of three soil series. Measurements of the pressure difference across the soil core at varying flow rates were used to calculate gas permeability (k), from soil having a range of soil gasfilled porosities (Ea). Bulk density, pore‐size distribution, and particle‐size distribution were also measured on each soil. In soils containing <20% clay, the relationship between the gas‐filled porosity and the gas permeability was adequately represented by a linear equation across the range (0.4–33%) of gas‐filled porosities tested. The linear equation was unique to each soil studied and a general equation representative of all soils could not be established. Structured soils exhibited greater permeabilities than poorly structured soils, presumably due to the larger inter‐aggregate flow channels characteristic of structured soils. In poorly structured soils, finer textures were less permeable than coarser textures. Three of four soils with <20% clay exhibited anisotropic behavior, with higher permeabilities in the horizontal direction than in the vertical direction, related to their alluvial origin.
Interface Penetration Model Formulation for Analyzing Wall‐Separation‐Influenced Transient Hydraulic Conductivity Data
Authors: Jennings Aaron A. , Ravi Varadhan 
Published: July 2010

AbstractHydraulic conductivity values measured in permeameters can be influenced by the formation of preferential flow pathways that allow a significant fraction of flow to bypass the soil sample. Problems of this type are of particular concern when testing low‐permeability soils with aggressive permeants because reactions increase the possibilities for preferential flow pathways to develop. A wall‐separation preferential flow model is proposed based on the discrete interface penetration (DIP) modeling strategy. The formulation is specifically designed to help determine if observed transient hydraulic conductivity behavior may be attributed to soil‐permeant interactions, or may have resulted from a wall separation preferential flow pathway that developed after the start of the permeameter experiment. Analytical solutions are presented for two sets of boundary conditions. Example evaluations of experimental data are presented to illustrate how these solutions could be applied. Information is also presented on model parameter estimation and sensitivity. Possible extensions of the modeling strategy to additional problems of preferential flow are also discussed.