bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology, Porosity, and Hydraulic Conductivity of Weathered Granitic Bedrock and Overlying Soils
Authors: Graham R. C. , Anderson M. A. , Sternberg P. D. , Tice K. R. , Schoeneberger P. J. 
Published: July 2010

AbstractGranitic bedrock, generally weathered several meters deep, is widespread in upland areas of California. Sound management of these areas requires knowledge of the hydraulic properties of both soils and weathered bedrock. The objectives of this research were to determine the saturated hydraulic conductivity (Ksat) of weathered granitic bedrock and overlying soils and to relate the measured Ksat to the regolith morphology and porosity. The study sites in the foothills of the San Jacinto Mountains represent common regolith conditions in granitic terrain of southern California: a coarse‐loamy Entisol <50 cm thick and a fine‐loamy Alfisol ≈ 100 cm thick, both over weathered granitic rock. The underlying bedrock (Cr horizon) at each site has a low clay content (<6%) and is weathered such that chunks of it can be excavated by chopping with a spade and crushed into grains using bare hands. In situ Ksat, measured using constant‐head permeameters, was highest (29 cm h−1) in the Entisol AC horizon, which also had the greatest macrovoid (>0.1 mm diam.) space (24%), a low clay content (6%), and abundant roots to provide pore continuity. A pedogenic horizon also had the lowest Ksat, with the Alfisol Bt horizon averaging 0.9 cm h−1. This horizon had 9% macrovoid space and 21% clay. The Cr horizons had intermediate Ksat values (1.4–3.7 cm h−1). Low clay contents, joint traces, and macrovoids (7–9%) largely unimpeded by illuvial clay help make weathered granitic bedrock an effective conductor of water under saturated conditions. On a landscape scale, water should percolate readily into regolith on Entisol sites, whereas runoff is more likely on Alfisol sites due to the low Ksat of the Bt horizon.
Derivation of Soil Properties Using a Soil Land Inference Model (SoLIM)
Authors: Zhu A‐Xing , Band Lawrence , Vertessy Robert , Dutton Barry 
Published: July 2010

AbstractSoLIM (Soil Land Inference Model) is a fuzzy inference scheme for estimating and representing the spatial distribution of soil types in a landscape. This study developed the inference method a step further to derive continuous soil property maps through two case studies. The first case illustrates the derivation of soil A horizon depth in a mountainous area in western Montana. It was found that the inferred depths are a closer fit to observed depths than those derived from the conventional soil map at both spatial and attribute levels. The second case shows the derivation of soil transmissivity values across a small catchment with a gentle environmental variation in Tumut, NSW, Australia. This case shows that the derived soil transmissivity map is comparable to the results from systematic field survey over a small area. SoLIM works well in an area where there is a good understanding of the relationships between soils and their formative environment and where the soil formative environment can be characterised using current geographical information system techniques. However, we experienced difficulty with the methodology when it was applied in an area where the environmental gradient is gentle and the soil formative environment cannot be very well described using the primitive environmental indices currently employed in SoLIM.
Chemical and Mineralogical Conversion of Andisols following Invasion by Bracken Fern
Authors: Johnson‐Maynard J. L. , McDaniel P. A. , Falen A. L. , Ferguson D. E. 
Published: July 2010

AbstractAndisols support ≈200 000 ha of mid‐elevation grand fir (Abies grandis [Dougl. ex D.Don] Lindl.) forests in the Pacific Northwest region that are characterized by little or no natural conifer regeneration following removal of the forest canopy. Previous work suggests that the properties of these Andisols have been altered as a result of the establishment of successional communities dominated by bracken fern (Pteridium aquilinum [L.] Kuhn) in deforested areas. In this study, we compared soil properties in a 30‐yr‐old bracken fern site (clear‐cut in 1965), a natural bracken fern site that is estimated to be centuries old, and an adjacent undisturbed forest in the Clearwater National Forest of northern Idaho. Results indicate that changes in chemical properties have accompanied establishment of successional communities. Mean weighted pH within the ash cap of the 30‐yr‐old bracken fern site (4.6) is significantly lower than that of the undisturbed forest (5.2). Mean values for Al saturation range from 27% in the undisturbed forest to 52% in the 30‐yr‐old bracken fern site; organic C is also lower in the undisturbed forest (37 g/kg) than in the 30‐yr‐old bracken fern site (54 g/kg). The dominant secondary mineralogical component of soils of the undisturbed forest is inorganic, short‐range‐order Al‐Fe minerals, while metal‐humus complexes are dominant in the bracken‐fern‐influenced soils. Data indicate that bracken fern successional communities are responsible for a shift from allophanic to nonallophanic properties in these soils, probably due to increased levels of soil organic C associated with bracken fern and a subsequent increase in formation of Al‐humus complexes. Furthermore, such a mineralogical shift may contribute to the observed problems with conifer regeneration.
Polymer Effects on Water Infiltration and Soil Aggregation
Authors: Ben‐Hur M. , Keren R. 
Published: July 2010

AbstractThe effectiveness of synthetic polymers as soil conditioners was found to depend on polymer properties. We hypothesized that the polymer penetration and movement into the aggregate are important factors in reduction of surface sealing. The effect of nonionic (P‐101), cationic (CP‐14), and anionic [Complete Green (CG)] commercial polymers on infiltration rate (IR) and aggregate formation was studied in a sandy loam (Typic Rhodoxeralf). Amounts of 25, 50, and 75 kg ha−1 of each polymer were spread across the soil surface. After air drying, the surface was subjected to 68 mm of distilled water with impact energy of 18.1 J mm−1 m−2 using a rainfall simulator. Soil particle association was studied in 10% (w/v) soil suspension with polymer concentration ranging from 0 to 50 g m−3. Viscosity values 3.3 109, and 165 mPa s were determined in 5 g L−1 of P‐101, CP‐14, and CG solutions at shear rate of 27 s−1, respectively. The final IR values were 63 to 30 mm h−1 at P‐101, 18 to 24 mm h−1 at CP‐14, and 18 to 30 mm h−1 at CG, compared with 8 mm h−1 in untreated soil. The critical time values in suspensions with different concentrations of polymer were 4.3 to 2.7 min for P‐101, 1.0 to 3.4 min for CP‐14, and 1.0 min for CG. The critical time indicates the size of the aggregate formed in a suspension; the lower the critical time, the larger the aggregates. It was suggested that because the particle surfaces are exposed to polymer molecules in suspension, the large molecule of CG could tie more suspended particles to form aggregates. The greater effectiveness of P‐101 in preventing sealing was probably due to its ability to penetrate into aggregates, because of its small molecular size and low viscosity in solution.
Stability and Transportability of Water‐Dispersible Soil Colloids
Authors: Seta A. K. , Karathanasis A. D. 
Published: July 2010

AbstractColloid migration in subsurface environments has attracted special attention lately due to its suspected role in facilitating transport of contaminants to groundwater. This study was conducted to evaluate the stability and potential transport of water‐dispersible colloids (WDC) through intact soil columns, and the properties of colloids and soil columns facilitating or retarding colloid stability and transportability. Water‐dispersible colloids were fractionated from six representative soil samples with diverse mineralogy and physicochemical characteristics. Their stability was evaluated from settling‐rate experiments at different pH levels. The results demonstrated that colloid stability was pH dependent. Colloid transportability was assessed by introducing colloid suspensions at a constant flux into intact soil columns representing upper Bt horizons of a Maury (fine, mixed, mesic Typic Paleudalf) and a Loradale (fine‐silty, mixed, mesic Typic Argiudoll) soil and evaluating characteristics of the suspensions that were eluted. After five pore volumes of leaching, colloid recovery in the eluents ranged from 35 to 90% depending on type of colloid, initial concentration in the influent, and soil column. The mineralogical composition of the colloid, which was correlated with particle size, appeared to have a profound effect on colloid transportability, following the sequence smectitic > mixed > kaolinitic. Total exchangeable bases (TEB) and pH of WDC also significantly influenced colloid transport. Increasing colloid concentration in the influent slightly increased colloid transportability. Soil columns with better macroporosity and less surface charge (Maury) transported more colloids than soil columns with less macroporosity and higher surface charge (Loradale).
Atrazine Adsorption by Soil Colloids and Co‐Transport through Subsurface Environments
Authors: Seta A. K. , Karathanasis A. D. 
Published: July 2010

AbstractThis study evaluated the potential of water‐dispersible soil colloids with diverse physicochemical and mineralogical characteristics to adsorb and mediate the transport of atrazine through macropores of intact soil columns. The soil columns were taken from the upper solum of an Alfisol (Maury) and a Mollisol (Loradale) in the Bluegrass region of Kentucky. Six different colloid suspensions mixed with atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] were introduced at a constant flux into the undisturbed soil columns. The eluents were collected and analyzed periodically for colloid and herbicide concentrations. Colloid recovery in the eluents ranged from 45 to 90%. The presence of colloids enhanced the transport of atrazine by 2 to 18%, depending on colloid type and mobility. Colloids with higher pH, total exchangeable bases (TEB), cation‐exchange capacity (CEC), organic carbon (OC), surface area (SA), and electrophoretic mobility (EM), showed greater mobility, greater affinity for atrazine, and greater potential to co‐transport atrazine. In contrast, increased levels of kaolinite, Fe, and Al inhibited atrazine adsorption and transport. Soil columns with higher hydraulic conductivity, well‐developed macropore system, and lower surface reactivity (Maury) also transported more atrazine. In spite of the increased transportability of atrazine by the presence of soil colloids, the colloid‐bound herbicide fraction contributed ≤1% to the observed increase. This suggests that matrix‐surface‐site exclusion and blocking mechanisms induced by the presence of colloids are more important than colloid sorption in promoting atrazine mobility in subsurface soil environments.
Arsenic Availability in Soil with Time under Saturated and Subsaturated Conditions
Authors: Onken B. M. , Adriano D. C. 
Published: July 2010

AbstractLoss of As from solution in reduced soils has long been attributed to volatilization of As as arsines. This study was conducted to determine whether loss of As from soil solution could be accounted for by increases in surface‐bound forms of As. Pickney sand (sandy, siliceous, thermic Cumulic Humaquept) was treated with sodium arsenate and sodium arsenite and incubated under saturated and subsaturated conditions for up to 68 d. Sequential extraction of As by NH4Cl, NH4F, NaOH, and H2SO4 was performed to monitor the redistribution of As between different fractions with time. By determining the As concentration present in sequentially extractable forms, it was demonstrated that As became more recalcitrant in soil with time. Arsenic added in water‐soluble form became more tightly bound to the soil as evidenced by the necessity of stronger extractants to remove added As. The conversion (curing) of As to more insoluble forms occurred in saturated soils where the pe/pH status was in the arsenite stability field and in subsaturated soils where the pe/pH status was in the arsenate stability field. The rate at which As was converted to more insoluble (and possibly less bioavailable) forms was as rapid in saturated soils as in unsaturated soils. Arsenic was conserved during the experiment with no apparent loss of As from the system through 68 d.
Estimation of Map Unit Composition from Transect Data
Authors: Young Fred J. , Hammer R. David , Williams Frederick 
Published: July 2010

AbstractWe are concerned with the documentation of taxonomic variability within soil survey map units, and how that variability is expressed statistically. Twelve randomly selected transects were used to sample soil properties and classify pedons within a fluvial map unit of the Boone County, Missouri, soil survey. Map unit taxonomic variability was high, with 28 taxonomic family classes. Twenty‐five percent of the sampled soils were in the named taxonomic class of the map unit, but most were similar inclusions. Interpretive purity of the sample was 83%. Variances about this sample proportion were calculated using three methods: (i) simple random sampling, (ii) cluster sampling, and (iii) two‐stage random sampling. The simple random sampling formula provided the smallest variance, compared with the cluster formula (55% larger) or the two‐stage formula (72% larger). However, the interpretation of transect sampling as simple random sampling is questioned. The two‐stage random sampling method seemed most conceptually correct, but is computationally intensive and requires questionable assumptions about the population size. Confidence intervals based on small sample sizes drawn from binomial populations are highly suspect, and perhaps should be referred to as “approximate bounds”. It is important to carefully consider the assumptions and effects of any statistical technique chosen to analyze map unit composition.
Tillage Mulch Depth Effects during Fallow on Wheat Production and Wind Erosion Control Factors
Authors: Schillinger William F. , Papendick Robert I. 
Published: July 2010

AbstractBlowing dust from summer fallow is a major soil loss and air quality concern in winter wheat (Triticum aestivum L.) production areas of the inland Pacific Northwest (PNW). The objective of our 3‐yr on‐farm study in a 286‐mm precipitation zone in eastern Washington was to determine the effects of tillage mulch depth during fallow on surface soil roughness, residue retention, seed‐zone water storage, wheat establishment, and grain yield. Soil is a Ritzville silt loam (coarse‐silty, mixed, mesic Calcidic Haploxeroll). Mulch depth combinations were created by primary spring tillage with noninversion implements at 100‐ or 160‐mm depths, and with subsequent rodweedings at 50‐ or 100‐mm depths. Tillage mulch depth during fallow did not affect seedling emergence after two wet fallow cycles, but wheat spike density was consistently greatest in deep‐tilled plots. In a dry fallow cycle, when dry soil extended beneath the rodweeder or secondary tillage layer, deep tillage increased stand establishment from 30 to 62 seedlings m‐2, grain yield from 4.4 to 5.3 Mg ha‐1, and residue production from 5.7 to 8.4 Mg ha‐1 compared with shallow tillage. Surface soil clods >50‐mm diameter, desirable for wind erosion control, increased with tillage mulch depth from 14 to 21 Mg ha‐1 in 1994, and from 22 to 37 Mg ha‐1 in 1995. A drawback to deep tillage mulches was the need to reduce tractor speed during planting. Surface residue retention was not affected by tillage mulch depth. Results show that surface clod structure and roughness during fallow can be maintained to protect the soil from erosion, mostly benefiting wheat production potential.
Estimating the Least Limiting Water Range of Soils from Properties and Management
Authors: da Silva Alvaro Pires , Kay B. D. 
Published: July 2010

AbstractThe least limiting water range, LLWR, is the range of soil water content within which plant growth is least limited by water potential, aeration, and mechanical resistance. Little information is available on the influence of soil property or management practice on LLWR. The LLWR calculation is based on the water release curve (WRC) and the soil resistance curve (SRC). This study tested the hypothesis that pedotransfer functions (PTF) that describe the influence of soil properties and tillage on the WRC and the SRC could be used to assess the influence of these factors on the LLWR. Thirty‐two paired sampling sites were located along two parallel transects in a side by side comparison of no‐till and conventional tillage. The transects crossed three soil types: Aquic Hapludalf, Psammentic Hapludalf, and Typic Hapludalf. Clay content (CLAY) varied from 5.8 to 37.4%, organic carbon (OC) varied from 9 to 39 g kg‐1, and the bulk density (Db) varied from 0.96 to 1.71 g cm‐3. Multiple regression analyses showed that WRC was related (R2 = 0.94) with CLAY, OC, and Db whereas the SRc was related with CLAY and OC (R2 = 0.86). Tillage had no independent effect in either of the two functions. Values of LLWR, calculated from the PTF, varied from 0 to 0.3093 cm3 cm‐3. The LLWR was negatively related with CLAY and Db and positively related with OC. The analyses supported the hypothesis illustrating the value of PTF in assessing the sensitivity of LLWR to soil properties.
Quantitative Soil‐Landscape Modeling for Estimating the Areal Extent of Hydromorphic Soils
Authors: Thompson James A. , Bell James C. , Butler Charles A. 
Published: July 2010

AbstractThe spatial distribution of hydromorphic soils across the landscape affects soil survey, broad‐scale wetland identification, and ecological studies. The change from upland to wetland is frequently difficult to delineate because it often occurs along a gradual continuum. We have developed a color index, the Profile Darkness Index (PDI), to assist in making these delineations. The PDI is well correlated with the duration of saturated and reducing conditions in specific Mollisol catenas in humid regions of the north‐central USA. The objective of this research was to use soil‐landscape modeling techniques to relate the variation of PDI to terrain attributes that describe the flow and accumulation of water on hillslopes. Regression models that quantify the relationships between terrain attributes and PDI on a hillslope in west‐central Minnesota indicate that variability in slope gradient, profile curvature, and elevation above local depression explained up to 65% of the variability in PDI. These models may be used to estimate the areal extent of hydromorphic soils using terrain attributes derived from a high‐resolution (10‐m resolution) digital elevation model and to quantify relationships between spatial variability of terrain attributes and of PDI. Knowledge of the terrain attributes that are statistically important according to these models, and their relative effects on PDI (e.g., as slope gradient decreases, PDI increases) may be applied to field‐scale delineations of hydric soils.
Carbon Isotope Ratios of Great Plains Soils and in Wheat‐Fallow Systems
Authors: Follett R. F. , Paul E. A. , Leavitt S. W. , Halvorson A. D. , Lyon D. , Peterson G. A. 
Published: July 2010

AbstractThe purposes of this study were to improve knowledge of regional vegetation patterns of C3 and C4 plants in the North American Great Plains and to use δ13C methodology and long‐term research sites to determine contributions of small‐grain crops to total soil organic carbon (SOC) now present. Archived and recent soil samples were used. Detailed soil sampling was in 1993 at long‐term sites near Akron, CO, and Sidney, NE. After soil sieving, drying, and deliming, SOC and δ13C were determined using an automated C/N analyzer interfaced to an isotope‐ratio mass spectrometer. Yield records from long‐term experimental sites were used to estimate the amount of C3 plant residue C returned to the soil. Results from δ13C analyses of soils from near Waldheim, Saskatchewan, to Big Springs, TX, showed a strong north to south decrease in SOC derived from C3 plants and a corresponding increase from C4 plants. The δ13C analyses gave evidence that C3 plant residue C (possibly from shrubs) is increasing at the Big Springs, TX, and Lawton, OK, sites. Also, δ13C analyses of subsoil and topsoil layers shows evidence of a regional shift to more C3 species, possibly because of a cooler climate during the past few hundreds to thousands of years. Data from long‐term research sites indicate that the efficiency of incorporation of small‐grain crop residue C was about 5.4% during 84 yr at Akron, CO, and about 10.5% during 20 yr at Sidney, NE. The 14C age of the SOC at 0‐ to 10‐cm depth was 193 yr and at 30 to 45 cm was 4000 yr; 14C age of nonhydrolyzable C was 2000 and 7000 yr for these same two respective depths. Natural partitioning of the 13C isotope by the photosynthetic pathways of C3 and C4 plants provides a potentially powerful tool to study SOC dynamics at both regional and local scales.
Runoff and Soil Loss Response to Vegetation Removal in a Semiarid Environment
Authors: Castillo V. M. , Martinez‐Mena M. , Albaladejo J. 
Published: July 2010

AbstractThe removal of vegetation is the main cause of soil degradation in semiarid areas. We hypothesized that the changes in soil properties induced by vegetation removal modified the runoff and soil erosion response in a semiarid area of Spain. To test this, two plots (15 by 5 m) were installed on a 23% slope on a Lithic Haploxeroll. Vegetation was removed by clipping from one of the plots (Plot D) and the changes in surface runoff and soil loss were compared with an undisturbed control plot (Plot N) from 1989 to 1993. Total runoff was significantly greater in Plot D (48.8 mm) than in Plot N (34.9 mm). Runoff ratios between the disturbed and natural plots increased with time from 1.4:1 in 1990 to 2.5:1 in 1993. Vegetation removal increased the soil losses in Plot D (150.2 g m−2) by 127% compared with those in Plot N (66.3 g m−2). The annual soil loss ratio between the disturbed and natural plots increased from 1.6:1 in 1989 to 4.2:1 in 1993. The observed increase in surface runoff and soil loss was attributed to a progressive deterioration of soil physical properties in Plot D. Bulk density increased by 8.4% (from 1.55 to 1.68 Mg m−3) and a reduction of total organic carbon (from 4.0 to 2.6%) and the percentage of stable aggregates (from 81.6 to 56.3%) were observed. There was no evidence of vegetation recovery, suggesting that reduced vegetal cover might lead to irreversible soil degradation in semiarid areas.