bluuebunny/crossref_metadata_2025_split huggingface dataset:
Incorporation of a Wide Variety of Organic Substrate Carbons into Soil Biomass as Estimated by the Fumigation Procedure
Authors: Kassim G. , Martin J. P. , Haider K. 
Published: July 2010

AbstractBiodegradation of the carbon or specific carbons of a large variety of 14C‐labeled organic substrates were followed in a closed, constantly aerated system in Steinbeck loam (pH 5.0) and Greenfield sandy loam (pH 7.0) over various periods of incubation at 22°C. Incorporation into biomass and stabilization in humus were estimated after 12 weeks of incubation. The labeled carbons in biomass were estimated using a slight modification of Jenkinson's fumigation method. Readily available substrates such as glucose, acetate, pyruvate, uracil, uridine, amino acids, and some polysaccharides were rapidly metabolized by the soil population, and after 8 to 12 weeks, about 80% or more of the substrate carbons had evolved as CO2. After 12 weeks, about 20 to 40% of the residual carbons of these substrates were present as hiomass, and 60 to 80% was present as new humus. Glucosamine, cysteine, cellulose, protein, and some microbial and plant polysaccharides were degraded to a somewhat smaller extend, 60 to 70%, indicating some stabilization of the intact molecules or partial degradation products by incorporation into humus or by complexing with soil colloids or metals. About 10 to 30% of the residual carbons were associated with the biomass after 12 weeks. Most microbial cells and plant residues such as straw were utilized to a still lesser extent, with about 50 to 60% loss of applied C in 12 weeks and an incorporation of about 5 to 13% of the residual 14C into biomass. A fungal humic acid‐type melanin was still more resistant, and less of the residual C, 0.2 to 1.3%, was present in biomass at 12 weeks.
Comparison of Effects of Nitrate, Nitrite, and Nitric Oxide on Reduction of Nitrous Oxide to Dinitrogen by Soil Microorganisms
Authors: Gaskell J. F. , Blackmer A. M. , Bremner J. M. 
Published: July 2010

AbstractRecent work has shown that nitrate inhibits reduction of nitrous oxide (N2O) to dinitrogen (N2) by soil microorganisms under anaerobic conditions. Studies to investigate the possibility that this inhibition is caused by nitrite or nitric oxide (NO) formed through microbial reduction of nitrate showed that both NO and nitrite inhibit reduction of N2O to N2 by soil microorganisms under anaerobic conditions (helium atmosphere) but that the inhibitory effect of NO on N2O reduction is much smaller than the effects of nitrate or nitrite. Comparison of the effects of nitrate, nitrite, and mixtures of nitrate and nitrite on reduction of N2O to N2 by soils incubated under He showed that nitrate per se inhibits N2O reduction and did not confirm a recent suggestion that the inhibitory effect of nitrate on N2O reduction is due to nitrite formed through microbial reduction of nitrate.
Soil Properties Influencing Penetration Resistance of Canfield and Geeburg Soils
Authors: McCormack D. E. , Wilding L. P. 
Published: July 2010

AbstractPenetration resistance was measured in situ by the procedures of the ASTM standard penetration test. Selected horizons were tested at five sites of each of two soil series. Presumptive bearing value is shown to be influenced most strongly by soil moisture content, bulk density, and clay content. These variables explain 78% of the variation in presumptive bearing value.Soil strength as determined by this test and the vane shear tests were compared and found to be very similar; however, the penetration test is less sensitive to differences in soil moisture content. Determination of presumptive bearing value using the penetration test provides information useful to understanding the behavior of specific horizons of soil series.
Agricultural Erosion Indicated by 137Cs Redistribution: I. Levels and Distribution of 137Cs Activity in Soils
Authors: Brown R. B. , Cutshall N. H. , Kling G. F. 
Published: July 2010

AbstractModern agricultural erosion was studied using 137Cs fallout as an indicator of erosion and sedimentation in the hilly margin of the Willamette Valley, Ore. Objectives of this phase of the study were (i) to identify areas most severely eroded over the period of fallout (since early 1954), and (ii) to identify areas that had been subject to net deposition over the same period.Along each of eight transects, sampling sites were selected in ridgetop, steep sideslope, and concave footslope positions. Also sampled were a single convex ridge shoulder, a high ridgetop, two alluvial fans, two floodplain sites, and two sites in an 8‐year‐old pond. Soil cores were collected at each site and analyzed by depth increment for 137Cs activity.Depth distribution patterns of 137Cs activity suggested that fallout 137Cs was retained in surface soils and was, therefore, a good tracer in erosion/sediment studies. Depositional sites tended to have overthickened 137Cs profiles and high total contents of 137Cs. Average total 137Cs activity in depositional sites was about 12 pCi/cm2.Sideslopes and ridgetops, with average total 137Cs activities of about 8 pCi/cm2, were indistinguishahle from each other. Failure to distinguish sideslopes from ridgetops based on 137Cs signature was attributed to (i) widespread runoff from these lands, (ii) damping effects of plowing and continuing input of fallout 137Cs, and (iii) an apparent lack of erosion severe enough to have depleted preferentially the 137Cs‐rich surface soils of sideslopes.
Persistence of Potassium in Forest Systems: Further Studies with the Rubidium/Potassium Technique
Authors: Stone Earl L. 
Published: July 2010

AbstractFoliar samples from comparable potassium (K)‐fertilized and unfertilized plots of nine forest fertilization trials were analyzed for rubidium (Rb) and K. The trials represented different combinations of soils, species, age classes, and rates. Application of the Hafez and Stout Rb/K “reverse tracer” procedure demonstrated that in seven of the nine experiments, fertilizer K still made up 25 to 45% of total foliage K 4 to 12 years after application. Inconclusive results from the remaining trials were probably due to inappropriate sampling in one instance but are unexplained in the other.Overall results, in conjunction with previous reports, suggest that the Rb/K technique may be widely useful in studies of K retention and circulation in forest systems.
Analysis of Chamber Methods Used for Measuring Nitrous Oxide Production in the Field
Authors: Jury W. A. , Letey J. , Collins Tim 
Published: July 2010

AbstractTwo current procedures for measuring nitrous oxide (N2O) production in the field are studied using a two‐dimensional model of gas production and diffusion through soil. These procedures consist of trapping the gas as it leaves the soil surface, either by allowing the gas to build up in a closed chamber (closed cover), or by removing and measuring the gas as it leaves the soil (open cover). The model calculations suggest that in many cases, neither measurement relates well to the N2O production rate because the gas concentration is still building up in the soil. There are also expected differences between the two methods, with the closed cover measurement underestimating the flux from the soil when air contents are relatively high while production is occurring, if gas is allowed to build up in the chamber for more than a few hours.The calculations suggest that, due to the large phase lag caused by gaseous diffusion, the only way to obtain accurate information about the extent of N2O release to the atmosphere from the soil from a denitrification‐reduction event is to trap all gas which is produced by the process. This may require monitoring for up to several weeks after production ceases if soil water content remains high.
Modification of Buried Soils by Postburial Pedogenesis, Southern Indiana
Authors: Mausbach M. J. , Wingard Robert C. , Gamble E. E. 
Published: July 2010

AbstractThe integration of buried soils with overlying soils was evaluated by examining base saturation, clay illuviation, and the clay weathering products of soil formation. Base saturation is considered as a rapidly changing characteristic, clay illuviation as slow to change, and clay minerals as most resistant to alteration. The soils studied have loamy or clayey buried B horizons that overlie clastic or limestone rock of Mississippian age. Pedisediment or a zone of mixed loess and pedisediment separates a surficial loess from the buried Sangamon B horizon. Base saturation and fine clay distributions above clayey and loamy Sangamon B horizons show little change through the loess and pedisediment. This distribution of base saturation and fine clay indicates that the pedisediment is integrated with the ground soil.However, where the Sangamon B is clayey, trends in base saturation and fine clay distributions break abruptly at the buried B. Integration of the ground soil with the clayey Sangamon B is not indicated by these properties. When the buried horizons are loamy, there has been post‐loess leaching of bases and illuviation of clay. Apparently, clayey buried Bt horizons retard downward movement of solutes which effectively inhibits post‐loess alteration of the clayey Sangamon B horizon. Amounts and kinds of clay minerals are about the same in the pedisediment and Sangamon B, which indicates that post‐loess integration of the pedisediment has not proceeded to the extent of altering clay mineral suites.
Predicting Temperatures of Bare‐ and Residue‐covered Soils from Daily Maximum and Minimum Air Temperatures
Authors: Gupta S. C. , Radke J. K. , Larson W. E. , Shaffer M. J. 
Published: July 2010

AbstractThe manuscript describes a model for prediction of soil temperature of bare and various residue‐covered soils with and without a corn crop where the needed inputs are (i) daily maximum and minimum air temperatures at the 2‐m height, (ii) initial soil temperature, and (iii) thermal diffusivity profiles. This is a simplification of our earlier model and involves the replacement of measured hourly air temperature by an estimate.Predictions of root zone temperature from the current model are tested against the measured values for six treatments representing various degrees of cover resulting from either the residue or shading by growing plants. Ninety‐five percent of the daily predicted temperatures at the 5‐cm depth are within −5.3 to 7.1°C and −2.0 to 3.1°C of the measured values for bare soil and corn plus 50% residue‐covered soil, respectively. Differences between the predicted and measured root zone temperatures decreased with an increase in plant or residue cover at the surface and soil depth.Replacement of measured hourly air temperature by an estimate in the soil temperature model drastically reduces the amount of input data needed to predict root zone temperatures. The predicted temperatures are valuable as inputs for crop growth and nitrogen transformation modeling and in forecasting spring root zone temperatures for various plant or residue covers based upon forecasts of the daily maximum and minimum air temperatures. These predicted values of root zone temperatures can be useful in deciding the planting dates for the Northern Corn Belt States.
Soil Physical Properties as Affected by Soybean and Other Cropping Sequences
Authors: Fahad A. A. , Mielke L. N. , Flowerday A. D. , Swartzendruber D. 
Published: July 2010

AbstractInfiltration, water stability of soil aggregates, and water retention characteristics were measured on a Sharpsburg silty clay loam (Typic Argiudolls) in a 4‐year cropping sequence. The cropping systems include soybean (Glycine max L. Merr.), sorghum (Sorghum bicolor L. Moench), corn (Zea mays L.), and fallow, in various sequential cropping combinations.The influence of cropping systems on size distribution of water‐stable aggregates is indicated by the values of geometric mean diameter (GMD). The rank order of GMD for the soybean sequences was: soybean after fallow > soybean after sorghum > soybean after corn > continuous soybean. The low GMD of continuous soybean reflected the negative effect of soybean roots in building a stable soil structure. Cumulative infiltration after 4 hours of water application was 6, 13, 29, and 41 cm for continuous soybean, sorghum after soybean, fallow after soybean, and corn after sorghum, respectively. The low infiltration was associated with low macroporosity and decreased aggregate stability. Both Kostiakov's and Philip's equations fitted the infiltration data reasonably well statistically, but Kostiakov's equation was a better fit for the early and late stages of infiltration.
Dry Soil Aggregation as Influenced by Crop and Tillage
Authors: Armbrust D. V. , Dickerson J. D. , Skidmore E. L. , Russ O. G. 
Published: July 2010

AbstractSoil loss by wind erosion is greater in the spring due to higher wind velocities, loss of protective crop residues by tillage and decomposition, and overwinter changes in nonerodible soil aggregates. This study was conducted to determine the effect of crop species and tillage on soil aggregation. Plots of continuous winter wheat (Triticum aestivum L.), grain sorghum (Sorghum bicolor L. Moench), and soybean (Glycine max L. Merr.) with tillage treatments of mechanical, chemical, and combination of mechanical and chemical weed control were sampled for aggregate distribution, stability, and overwinter breakdown.Winter wheat plots contained more nonerodible aggregates (> 0.84 mm), and the aggregates were more aggregates from sorghum or soybean plots. Soybean plots were lowest in all three variables measured. Tillage‐treatment effects varied, with the chemical‐treated plots containing the most nonerodible aggregates and the mechanical‐treated plots having the most stable aggregates.
Soil Bulk Density Analysis in Three Dimensions by Computed Tomographic Scanning
Authors: Petrovic A. M. , Siebert J. E. , Rieke P. E. 
Published: July 2010

AbstractCurrent soil bulk densitometric techniques lack the precision to detect three‐dimensional changes in density in a nondestructive manner. The x‐ray transmission computed tomography (CT) scanner was evaluated as a tool to determine soil bulk density. This scanner is an advanced tool in diagnostic radiology used to obtain a nondestructive cross‐sectional representation of the human body. Typical accuracy and precision for CT scanners are known for materials like human tissue with a linear attenuation coefficient near water. Machine response was evaluated near the upper limit of the measurement range where denser materials, such as soil, are located.Scanner analyses of soil and glass bead‐air filled sphere samples that varied in bulk density from 0.14 to 1.64 g/cm3 revealed that a positive linear response occurred with increasing density. For the Metea sandy loam soil (Arenic Hapludalfs), this CT scanner was found to have precision in the order of 19 mg/cm3. Spatial resolution or the ability to distinguish between two objects in the scanning plane was found to range from 1.25 by 1.25 by 2 mm3 to 6.4 mm in diameter by 2 mm. The greater resolution was obtained when density within the sample varied greatly. Errors in data can occur as a result of certain machine artifacts; however, many of these can be avoided by relatively simple methods.It was concluded that the CT scanner can be used to determine soil bulk density with good three‐dimensional spatial resolution. This is a potentially promising tool for research in the areas of compaction, soil management, and cultivation.
Temperature Dependence of Unsaturated Hydraulic Conductivity of Two Soils
Authors: Constantz Jim 
Published: July 2010

AbstractPacked columns of Oakley sand (mixed, mesic Typic Paleudalfs) and Hanford sandy loam (mixed, nonacid, thermic Typic Xerorthents) were used to develop isothermal steady‐state fluxes. Soil matric potentials were measured and unsaturated hydraulic conductivities were calculated over a range of matric potentials at 2°, 25°, and 45° ± 0.5°C. In addition, water retention characteristics (to −100 kPa) were measured at these same temperatures for both soils. In this paper, the calculated results are compared to an equation that relates unsaturated conductivity to the intrinsic permeability, the relative permeability, and the viscosity of water. The equation considers viscosity to be the only parameter that changes with temperature. The results show a much greater temperature dependence in the unsaturated conductivity than would be predicted by this equation. The results indicate that the relative permeability may be a function of temperature. The temperature dependence of the soil water matric potential, surface tension, and diffuse double‐layer thickness are discussed in terms of their possible interaction with the unsaturated conductivity values obtained. A case is presented for further study to isolate these temperature‐sensitive parameters as well as additional parameters related to fluid flow path changes with temperature.
The Effect of Turfgrass Thatch on Water Infiltration Rates
Authors: Taylor D. H. , Blake G. R. 
Published: July 2010

AbstractA high water infiltration rate is important for high quality sports turfgrass areas. An understanding of the effect of thatch and grass plants on water infiltration is needed in order to improve the management practices used to maintain high rates. The objective of this study was to determine if a layer of thatch acts as a limiting layer to water infiltration on coarse‐textured sports turfgrass soils.The effect of a thatch layer on water infiltration rate was determined using laboratory packed sand columns and field turfgrass areas constructed using soil mixtures with high sand content. Data from both laboratory and field experiments demonstrated that after infiltration reaches a constant rate, a layer of thatch did not reduce the water infiltration rate. Initial infiltration rate for thatch‐covered sand, however, was lower than the sustained infiltration rate, while the initial infiltration rate into sand without thatch was much higher than the sustained infiltration rate. Initial infiltration rate was very low when sand was covered with a layer of dry thatch, but it increased to near the sustained rate within 10 minutes.
Evaporite Mineral Species in Mancos Shale and Salt Efflorescence, Upper Colorado River Basin
Authors: Whittig L. D. , Deyo A. E. , Tanji K. K. 
Published: July 2010

AbstractEvaporite mineral species associated with Late Cretaceous marine sedimentary formations in a selected region of the Upper Colorado River Basin were identified by x‐ray diffraction analysis. Mancos Shale, a major contributor of dissolved mineral salts to the Colorado River and several of its tributaries in the Upper Basin, contains abundant gypsum as the only detectable evaporite mineral. Salt efflorescence associated with the Mancos Shale, however, contains variable quantities of Ca, Na, and Mg sulfate evaporite species, including gypsum (CaSO4 · 2H2O), epsomite (Mg2SO4 · 10H2O), hexahydrite (MgSO4 · 6H2O), pentahydrite (MgSO4 · 5H2O), starkeyite (leonhardtite) (MgSO4 · 4H2O), kieserite (MgSO4 · H2O), loewite [Na4Mg2(SO4)4 · 5H2O], bloedite [Na2Mg(SO4)2 · 4H2O],mirabilite (NaSO4 · 10H2O), and thenardite [Na2SO4). The hydrated sulfates of Na and Mg, as very labile salts, are subject to change in response to relatively minor changes in temperature and moisture status. Dominant evaporite mineral species associated with a few localized seeps and springs emanating from the Late Cretaceous Mount Garfield formation of the Mesaverde group, overlying the Mancos Shale, include soda (Na2CO3 · 10H2O), trona (Na2CO3 · NaHCO3 · 2H2O), nahcolite (NaHCO3), and halite (NaCl). Origin of the evaporite mineral species and their significance in relation to salt loading of the Colorado River are discussed.
Hydrodynamic Dispersion Involving Cationic Adsorption During Unsaturated, Transient Water Flow in Soil
Authors: Laryea K. B. , Elrick D. E. , Robin M. J. L. 
Published: July 2010

AbstractThe analysis of hydrodynamic dispersion of solutes during one‐dimensional absorption (horizontal flow) of solution into soil columns is extended to solutes which interact with the soil particle surfaces. The exchange process involved is assumed to be instantaneous and is described by a nonlinear adsorption isotherm. The relevant equations are solved for the apparent longitudinal dispersion coefficient using a computer program written in system/360 CSMP.Experiments with a clay loam soil indicated that when a concentrated solution of potassium chloride (KCl) (1N) infiltrates into a Ca2+‐saturated soil, the apparent longitudinal dispersion coefficient is effectively velocity independent. This calculated coefficient reflects the possible combined effects of an immobile water fraction and salt exclusion.
A “Micro‐Lysimeter” Method for Determining Evaporation from Bare Soil: Description and Laboratory Evaluation
Authors: Boast C. W. , Robertson T. M. 
Published: July 2010

AbstractA new (“micro‐lysimeter”) method for estimating evaporation from soil consists of pushing a thin‐walled cylinder 76 mm in diameter into field soil, removing the soil‐filled cylinder from the field, closing the bottom to make it water‐tight, determining the mass of the micro‐lysimeter, replacing it in the field with its top surface even with the surrounding soil, leaving it exposed to environmental conditions for a period of time (typically 1 d), and redetermining its mass. Evaporation loss from the micro‐lysimeter is the difference between the two masses.The objective of this study is to quantify the systematic deviations of such micro‐lysimeters from reality in order (i) to determine how long a given micro‐lysimeter can be used before its soil must be discarded (and a new sample taken if further readings are desired), and (ii) to correct for systematic deviations. The deviations are quantified by comparing short micro‐lysimeters with effectively “infinitely long” ones. The deviation is influenced by the time that the micro‐lysimeter is exposed to environmental conditions and by the length of the soil sample. For a silty clay loam soil under evaporativity conditions ranging from 2 to 9 mm/d, the measurement error for micro‐lysimeters 70 mm in length is found to be < 0.5 mm for 1 or 2 d, depending on whether the initial soil condition is “wet” or “dry,” respectively (0.26 or 0.13 g of H2O per gram of dry soil in the top 20 mm).Hence, for many applications the method is valid for 1 or 2 d. Correction equations for deviations of up to 0.5 mm are given. The method requires little equipment and makes possible evaporation measurement under some conditions (for example, at large numbers of sites or in areas of partial crop shading) where micrometeorological, water balance, and traditional lysimetric methods are unpractical or impossible.
Nutrient Transport Inside and Outside the Root Rhizosphere: Theory
Authors: Cushman John H. 
Published: July 2010

AbstractThe root surface as an absorption mechanism is briefly reviewed and various absorption models are discussed, e.g., the Koshland kinetic and Michaelis‐Menten models.Differences in nutrient availability and transport between the root rhizosphere and bulk soil matrix are examined. The differences manifest themselves in the diffusion coefficients, buffering powers, soil mechanical structure, and nutrient solubility and production. The differences in nutrient transport properties between the rhizosphere and bulk soil matrix are shown to give rise to two coupled partial differential equations. These equations are analytically solved for four sets of boundary conditions. The solutions are used to compute total nutrient uptake by a growing root.