bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unconfined Compressive Strength of Some Streambank Soils with Herbaceous Roots
Authors: Kleinfelder Donald , Swanson Sherman , Norris Gary , Clary Warren 
Published: July 2010

AbstractStreambank stability requires that bank strength exceed destabilizing forces, including compressive forces from sources such as trampling and foot traffic. This study was conducted to determine the unconfined compressive strength associated with herbaceously rooted streambanks, and whether greater compressive strength is developed from greater root‐length density (length of roots per volume of sample) or specific plant communities. The unconfined compressive strength, root‐length density, plant community, and engineering soil characteristics were measured on 122 samples from six meadow stream reaches. Sample compressive strength emulated an elastic condition in highly rooted samples, and developed negligible compressive strength in samples containing very small amounts of roots. Additionally, compressive strength was found to increase nonlinearly with increases in very fine root‐length density (herbaceous roots <0.5 mm in diam.), and reached an apparent asymptote at 50 kPa. The greatest compressive strength was derived from samples dominated by Nebraska sedge (Carex nebrascensis Dewey). Correlations between unconfined compressive strength and engineering soil properties were mostly insignificant, primarily because samples were derived from unconsolidated alluvium. Stream morphology parameters showed little correlation to compressive strength, root‐length density, or other independent variables, suggesting other unmeasured factors may have an equal or greater influence on stream morphology. Herbaceous roots appear to supply most of the compressive strength and soil stability found in meadow streambanks, especially those dominated by Nebraska sedge.
Preventing Irrigation Furrow Erosion with Small Applications of Polymers
Authors: Lentz R. D. , Sojka R. E. , Carter D. L. , Shainberg I. 
Published: July 2010

AbstractSoil erosion is a serious problem threatening sustainability of agriculture globally and contaminating surface waters. The objective of this study was to determine whether low concentrations of anionic polymers in irrigation water would appreciably reduce irrigation furrow erosion on Portneuf silt loam (coarse‐silty, mixed, mesic Durixerollic Calciorthid), a highly erodible soil. Furrow slope was 1.6%, furrow length was 175 m, and irrigation rates ranged from 15 to 23 L min−1. Inflow during the first 1 to 2 h of the first 8‐h irrigation was treated. Subsequent irrigations were untreated. Polyacrylamide (PAM) or starch copolymer solutions were injected into irrigation water entering furrows at concentrations of 0, 5, 10, and 20 g m−3. Sediment loss from polymer‐treated furrows was significantly less than that of control furrows in the first (treated) and second (untreated) irrigations, but not in the fourth (untreated). The PAM provided better erosion control than the starch copolymer. Efficacy of PAM treatments varied depending on its concentration, duration of furrow exposure, and water flow rate. In the initial (treated) irrigation and at low flow rates, 10 g m−3 PAM reduced mean sediment load by 97% compared with untreated furrows. Residual erosion abatement in a subsequent irrigation, without further addition of PAM, was approximately 50%. The PAM increased net infiltration and promoted greater lateral infiltration. Effective erosion control was achievable for a material cost below $3 ha−1 irrigation−1.
Soil Salinity Assessment by Electromagnetic Induction of Irrigated Land
Authors: Hendrickx J. M. H. , Baerends B. , Raza Z. I. , Sadig M. , Chaudhry M. Akram 
Published: July 2010

AbstractThe purpose of this study was to characterize the variability and statistical distribution of electromagnetic induction measurements for salinity assessment on irrigated land. Such information is needed to optimize future sampling schemes. A detailed salinity survey was carried out with an electromagnetic device (Geonics EM38) in a representative experimental area of 37 ha near Faisalabad, Pakistan. The apparent electrical conductivity of the soil was measured at >3400 locations. In addition, a visual agronomic salinity survey was conducted. A linear relation between the standard deviation of the data and their means indicated that the salinity data were log‐normally distributed. Therefore, we recommend using log‐transformed data for statistical inferences. Geostatistical analysis of the log‐transformed data verified that the salinity of a field was principally determined by the irrigation management of the farmer. Significant salinity differences were found between abandoned, fallow, and cropped fields, but not between fields with different crops. We found that the electromagnetic induction meter (EM38) was in good agreement with the visual agronomic survey. The EM38 was superior because it had a better resolution, was more sensitive to salinity changes with depth and spatially, and could be conducted with or without a crop or at any stage of a crop. For random sampling schemes in our experimental area, the budgetary efficiency of the survey improved when entire fields rather than single points were selected for the survey. For salinity sampling with a stratified random sampling scheme, the strata can be based either on land use or on visually observed salinity status.
Soil Test Phosphorus Availability as Affected by Time after Phosphorus Fertilization
Authors: Esilaba A. O. , Eghball B. , Sander D. H. 
Published: July 2010

AbstractThe availability of fertilizer P in the soil decreases with time after fertilization. Routine soil tests or other estimates of plant‐available P should accurately reflect that change. The objective of this study was to determine the effect of the time fertilizer P is in contact with soil on the ability of commonly used soil tests to extract plant‐available P. Experiments were conducted to determine the relationship between available P as determined by A value and Bray and Kurtz P1 (BK), sodium bicarbonate (SB), and Mehlich no. 2 (ME) P soil tests. The A value was assumed to be the best available method of determining plant‐available P. Samples from an acidic Thurman loamy sand topsoil (sandy, mixed, mesic Udorthentic Haplustoll) and a calcareous Uly silt loam subsoil (fine‐silty, mixed, mesic Typic Haplustoll) were incubated with 0, 10, 20, 40, and 80 mg P kg−1 for 4, 8, and 20 mo at field‐capacity water content. After each incubation period, oat (Avena sativa L.) was planted and grown in the greenhouse with an additional 0, 10, and 20 mg P kg−1 labeled with 32P. The A value was determined for each incubation period and was correlated with the soil test results. Solubility products were also determined for each incubation P rate and period. After 4 and 8 mo of incubation, the BK, SB, and ME soil tests did not extract plant‐available soil P very accurately using the A value as a standard. After 4 mo of incubation, the SB soil test underestimated available P by as much as 50% on the Uly soil, while the BK soil test overestimated available P on the Thurman soil by 40%. Although there was no improvement after 8 mo of incubation, all three soil tests accurately extracted available P after 20 mo when fertilizer P and soil P appeared to have reached an equilibrium. Solubility equilibria analysis lacked adequate sensitivity to show different soil P compounds as affected by time of incubation. The results indicate large potential P fertilizer recommendation errors when soil samples are taken and analyzed prior to achieving equilibrium between applied fertilizer P and soil P.
On Particle‐Size Distributions in Soils
Authors: Wu Q. , Borkovec M. , Sticher H. 
Published: July 2010

AbstractMeasurements of soil particle‐size distributions have been performed down to 20‐nm radius using, beside classical methods such as sieving and sedimentation, mainly static and dynamic light scattering. The number of particles N per unit volume with a radius larger than r was found to follow a power law N α r−v with the exponent v = 2.8 ± 0.1. This exponent was observed in all soils investigated and can be interpreted as the fractal dimension of an underlying structure. The power law usually held over two to five decades of length scales. Below the lower cut‐off, typically located around 50 to 100 nm, the number of particles (≃ 1016‐1019 cm−3) remained roughly constant. Above the upper cut‐off, typically between 10 and 5000 µm, the distribution fell off much more steeply, possibly also like a power law with an exponent v = 5.4 ± 0.2.
Test of a Heat‐Pulse Probe for Measuring Changes in Soil Water Content
Authors: Bristow Keith L. , Campbell Gaylon S. , Calissendorff Kees 
Published: July 2010

AbstractThe maximum temperature rise measured at some distance from a line heat source can be used to determine the volumetric heat capacity and hence water content of porous media. We describe a simple heat‐pulse device for determining the volumetric heat capacity and hence water content of porous media. The device consists of three needle probes (0.813‐mm diam., 28 mm long) mounted in parallel. The heater probe contains a heating element while the sensor (mounted 6 mm from the heater) and reference probe (mounted 20 mm from the heater) contain thermocouples. The reference probe can be used to automatically correct for changes in background temperature. Measurements made at three depths during drying of a laboratory soil column yielded accurate changes in soil water content provided actual heater‐to‐sensor probe spacings were used in the calculations. We describe a simple procedure for checking on the probe spacings once the probes have been installed. These heat‐pulse devices should prove useful for monitoring wetting or drying changes in soil water under both laboratory and field conditions.
Unsaturated Transport Processes in Undisturbed Heterogeneous Porous Media: I. Inorganic Contaminants
Authors: Jardine P. M. , Jacobs G. K. , Wilson G. V. 
Published: July 2010

AbstractProlonged disposal of organic and inorganic waste in shallow land burial sites throughout the USA has prompted detailed investigations of subsurface contaminant transport processes. The fate and transport of contaminant leakage from pits, trenches, and cribs into the vadose zone via storm events is not well understood. The objective of this study was to investigate the thermodynamic and kinetic processes controlling the transport of inorganic contaminants in unsaturated, heterogeneous subsurface media. Large undisturbed columns were isolated from a proposed waste site consisting of fractured saprolite (weathered interbedded shale and limestone), and steady‐state nonreactive and reactive solute transport experiments were performed at a variety of pressure heads. Observed breaktbrough curves (BTC) for binary and ternary mixtures in the Co‐Sr‐Ca system were delayed relative to nonreactive Br BTC, indicating that the former tracers were adsorbed by the solid phase. Transport of the binary mixtures Co‐Ca and Sr‐Ca was predicted reasonably well with the equilibrium convective‐dispersive (CD) equation using independent measurements of all model parameters. However, application of the nonequilibrium or kinetic CD model to the observed Sr and Co binary data resulted in an improved description of contaminant transport. Cation‐exchange equilibria relationships on homogenized subsurface material, using both shake batch and miscible displacement methods, adequately described the thermodynamic processes that were prevalent during contaminant transport. These results suggest that preferential transport of reactive contaminants is negligible for the unsaturated conditions used in this study, and that the structured saprolite within the subsurface media is a chemically active constituent during reactive solute transport. Although the transport of contaminants in the ternary Co‐Sr‐Ca system exhibited many of the same features as the binary transport studies, an attempt to simulate the transport of contaminants in the ternary system as independent species was less than adequate.
Measurements of Free Zinc2+ Activity in Uncontaminated and Contaminated Soils Using Chelation
Authors: Ma Q. Y. , Lindsay W. L. 
Published: July 2010

AbstractMeasurement of free Zn2+ activity is important for understanding the mechanisms controlling Zn2+ solubility in soils. Free uncomplexed Zn2+ activities were measured using the chelation method in 12 uncontaminated soils and eight contaminated soils. The measured Zn2+ activities ranged from 10−9.97 to 10−6.49 M for the uncontaminated soils, and 10−8.11 to 10−2.26 M for the contaminated soils. They were inversely related to soil pH, with a correlation coefficient of 0.96 for the uncontaminated soils and 0.89 for the contaminated soils. The measured Zn2+ activities and pH for the uncontaminated and contaminated soils can be expressed as log(Zn2+) = (5.90 ± 0.24) − 2 pH and log(Zn2+) = (9.38 ± 0.74) − 2 pH, respectively. The measured Zn2+ activities in the uncontaminated soils were near that of franklinite (ZnFe2O4). The measured Zn2+ activities in the contaminated soils were close to those of Zn2SiO4 or ZnCO3 depending on the contaminated soils. Different solid phases may control Zn solubility in different soils depending on the sources of contamination and the soil.
Soil Organic Matter as Influenced by Crop Rotations and Fertilization
Authors: Campbell C. A. , Zentner R. P. 
Published: July 2010

AbstractFew studies conducted in western Canada have assessed how crop rotations and fertilization influence soil organic matter content on land that has been cropped for many years. We monitored soil organic matter in the 0‐ to 0.15‐ and 0.15‐ to 0.3‐m depths of a 24‐yr crop rotation experiment conducted on a medium‐textured Aridic Haploboroll in southwestern Saskatchewan. Prior to the study, the land had been in a hard red spring wheat (Triticum aestivum L.)‐fallow rotation for ≈50 yr. Only the 0‐ to 0.15‐m segment showed significant treatment effects. Due to good weather and crop yields in the first 15 yr, soil organic matter had increased under well‐fertilized annually cropped rotations, and it remained constant under fallow‐containing rotations and under continuous wheat receiving inadequate N fertilizer. Because of several dry years in the final 9 yr of the study, all rotations except a well‐fertilized, fallow‐winter cereal‐wheat system lost organic matter. Changes in organic matter were directly related to the amount of crop residues produced by these systems and their ease of eroding. Soil organic matter was inversely related to apparent N deficit (i.e., N exported in grain minus N applied as fertilizer). The fallow‐flax (Linum usitatissimum L.)‐wheat rotation receiving N and P fertilizer had the lowest soil organic matter, partly due to low production of crop residues by flax, partly to greater leaching of NO3, and partly due to some loss of flax residues blown from the plots. Soil organic matter in the well‐fertilized fallow‐winter cereal‐wheat rotation remained constant because its shorter fallow period reduced soil erosion, and due to its more efficient use of N, as evidenced by minimal leached NO3‐N.
Carbon and Nitrogen Distribution in Aggregates from Cultivated and Native Grassland Soils
Authors: Cambardella C. A. , Elliott E. T. 
Published: July 2010

AbstractLong‐term cultivation of grassland soils reduces soil organic C and N content and has been associated with a deterioration in the aggregate structure of the soil. This study examined the effects of bare fallow (moldboard plow), stubble mulch fallow (subtill), and no‐till fallow management on aggregate size distribution and aggregate organic C and N contents compared with a native (virgin) grassland soil. Aggregate size fractions were separated by wet sieving and the proportion of soil was quantified for each aggregate size class. Mineral‐associated (silt and clay) organic matter was isolated by dispersing aggregates in sodium hexametaphosphate and removing tbe sand and particulate organic matter (POM) by passing the dispersed aggregates through a 53‐µm sieve. The POM fraction is composed primarily of partially decomposed root fragments and has an average C/N ratio of about 16. A large proportion of the total soil dry weight (50–60%) was isolated in the small macroaggregate (250–2000 µm) size class. The native grassland soil was more stable than the cultivated soils when slaked, and the no‐till soil was more stable than the stubble mulch and bare fallow soil when slaked. Reduced tillage management is effective at increasing the proportion of macroaggregates and results in the accumulation of wheat (Triticum aestivum L.) derived POM within the aggregate structure compared with bare fallow soil. It has previously been shown that the POM fraction accounts for the majority of the soil organic matter (SOM) initially lost as a result of cultivation of grassland soils. The data reported in this study relates the loss of structural stability from cultivation to losses of organic C and N from the POM fraction.
Short‐Term Effects of Surface‐Applied Gypsum on Revegetated Sodic Bentonite Spoils
Authors: Schuman G. E. , Meining J. L. 
Published: July 2010

AbstractThe high clay content and saline‐sodic characteristics of bentonite mine spoils result in an environment that is not conductive to sustainable plant growth. Use of wood residue amendments have enabled revegetation of these materials; however, sodic conditions persist or worsen, threatening the long‐term sustainability of these revegetated lands. Gypsum, 56 Mg/ha, was surface applied to these revegetated ecosystems to evaluate its effectiveness in ameliorating the spoil sodicity under a natural precipitation environment. The gypsum treatment significantly reduced the exchangeable Na and the exchangeable Na percentage of the 60‐cm spoil profile 3 yr after treatment. The gypsum amendment also significantly increased the spoil‐water storage in the 60‐cm spoil profile. Gypsum treatment resulted in a significant increase in the spoil electrical conductivity; however, this increase did not detrimentally affect the vegetation. Surface‐applied gypsum amendment effectively ameliorated the revegetated bentonite mine spoil sodicity under natural rainfall conditions in a semiarid environment.
Urea Nitrogen Budget for a Subarctic Agricultural Soil
Authors: Knight C. W. , Sparrow S. D. 
Published: July 2010

AbstractUrea is the predominant form of fertilizer N used in Alaska. However, little information is available on the N‐recovery efficiency (NRE) or the ultimate fate of urea‐N in subarctic soils. This study was conducted to determine the NRE and the ultimate fate of urea‐N applied in the spring for barley (Hordeum vulgare L.) production in interior Alaska. Urea and Ca(NO3)2 were applied at 100 kg N ha−1 and either incorporated into or left on the soil surface in each of three cropping years. Also, 15N‐labeled urea was applied to small plots. Ammonia traps and soil and plant samples were used to track the form and movement of the applied N. Ammonia volatilization losses were negligible. Deep soil samplings indicated negligible leaching of N. The NRE, as determined by the difference method, was estimated to be about 60% for urea and 73% for Ca(NO3)2. By the isotope dilution method, NRE for urea was calculated to be about 41%. An apparent added nitrogen interaction (ANI) accounted for an additional 16.5%. Approximately 43% of the applied urea‐N was recovered in the soil organic matter at the end of the season, 1% remained in the soil as inorganic N, and 15% was unaccounted for and assumed lost through denitrification. Grain yields did not differ due to N source or placement, but total plant N uptake was greater from the Ca(NO3)2 than from the urea source. Nitrogen placement did not affect N uptake. Fertilizer N cycling in this subarctic soil did not differ greatly from fertilizer N cycling in more temperate regions.
Optimization of Hydraulic Functions from Transient Outflow and Soil Water Pressure Data
Authors: Eching S. O. , Hopmans J. W. 
Published: July 2010

AbstractInverse solution techniques currently used for estimating unsaturated soil hydraulic functions from laboratory outflow experiments use cumulative outflow only in combination with initial and final soil water pressure head values. Additional soil water information is needed to improve the estimation procedure and to minimize uniqueness problems. It was the objective of this study to experimentally explore the feasibility of using both cumulative outflow and soil water pressure head data in the inverse solution for laboratory determination of soil hydraulic functions using both one‐step and multistep outflow experiments. Soil water pressure head was measured with a microtensiometer and pressure transducer. Desorption experiments were performed under both pressure and suction for the following soils: Yolo silt loam (fine‐silty, mixed, nonacid, thermic Typic Xerorthent), Panoche loam (fine‐loamy, mixed [calcareous], thermic TypicTorriorthent), Hanford sandy loam (coarse‐loamy, mixed, nonacid, thermic Typic Xerorthent), and Oso‐Flaco fine sand (coarse‐loamy, mixed Typic Cryorthod‐fine‐loamy, mixed, mesic Ustollic Haplargid). Water retention curves optimized from cumulative outflow alone were compared with those obtained from outflow and soil water pressure head measurements for both one‐step and multistep outflow experiments. Computer optimization of the retention curve by the inverse solution technique using transient outflow experiments was greatly improved when cumulative transient outflow data were combined with simultaneously measured soil water pressure head data. Pressure and suction experiments yielded equally good results for one‐step and multistep desorption. Moreover, the addition of soil water pressure head data resulted in unique parameter values for the optimized soil hydraulic functions under our experimental conditions.
Sorption of Trace Organics to Colloidal Clays, Polymers, and Bacteria
Authors: Bengtsson Göran , Lindqvist Roland , Piwoni Marvin D. 
Published: July 2010

AbstractSorption to dissolved macromolecules and colloidal particles may enhance the transport of environmental contaminants in subsurface environments. Some properties of sorbent and solute that may influence the adsorption behavior, especially in saturated soils with low organic C concentrations, were examined in a series of stirred reaction cell experiments, using acetophenone and ionizable 4‐chloroaniline and pentachlorophenol as solutes and substituted bio‐ and geopolymers and suspended clays as sorbents. The distribution coefficient was most variable, by a factor of 5500 from one sorbent to another, for the anionic pentachloropbenol and least variable, by a factor of 250, for acetophenone. These variations could be ascribed to differences in binding properties of the solute and sorbent functional groups. Sorption to clay minerals was generally low and approximated sorption to an aquifer soil suspension; the exception was a local clay with 12% organic C, which increased sorption of the phenolate ion more than 30 times compared with the low‐organic‐C clays. The most efficient sorbent was cells of bacteria isolated from aquifer material. The linear distribution coefficient for sorption on bacteria varied from 0.5 × 103 mL g−1 for acetophenone to 5 × 104 mL g−1 for neutral pentachlorophenol. The implications of sorption varying with solute and sorbent functional groups on movement of solutes through an aquifer were examined by a transport model, which divides the mobile system into an aqueous and a colloidal phase. The relative mobility of pentachlorophenol associated with colloidal sorbents can vary by as much as 90% as a result of variations of the distribution coefficient to the polymers and clays examined.