bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulated Aerobic Pedogenesis in Pyritic Overburden with a Positive Acid—Base Account
Authors: Doolittle James J. , Hossner L. R. , Wilding L. P. 
Published: July 2010

AbstractReclamation of surface‐mined land is often hindered by the excess salts and acidity produced by the weathering of pyritic overburden. This study was conducted to document the initial transformations that occur when pyritic overburden containing excess acid neutralizing potential is used as parent material in minesoil construction. An overburden containing 0.8% FeS2 (pyrite) and 1.6% inorganic carbonate (predominantly dolomite) was collected from the highwall of an active lignite surface mine in Panola County, Texas. The overburden was lightly crushed through a 13‐mm sieve and packed into three replicate lysimeters (0.75 by 0.75 by 1.2 m). The lysimeters were leached monthly with 63.5 mm of deionized water for 24 mo. The initial material had a pH of 8.3 and an excess acid neutralizing potential. Progressive FeS2 oxidation released H2SO4 and the pH decreased to 6.8. The dolomite dissolved, neutralizing the acidity, with subsequent release of Ca and Mg ions into solution. Leachate Ca2+ and SO2−4 concentrations exceeded the ion activity product of gypsum in the lower 60 cm of the lysimeters. Thin‐section analysis revealed that gypsum crystals precipitated along margins of residual pyrite particles and in conductive vughs and channels. The continued accumulation of gypsum in minesoil development could eventually lead to the formation of a gypsic or a petrogypsic horizon. A restrictive layer such as this would decrease vertical movement of water and O2, which would reduce vegetative growth, increase runoff and erosion, and thus increase the probability of reclamation failure.
Transport of Solutes as Affected by Irrigation Method
Authors: Jaynes D. B. , Rice R. C. 
Published: July 2010

AbstractThe leaching behavior of agricultural chemicals depends on the application method of both the chemical and water. This study investigated the leaching behavior of conservative tracers under intermittent flood and drip irrigation on a clay loam soil. Slug applications of conservative tracers were applied sequentially to a single 37‐m2 plot and leached under the two irrigation regimes with the same daily application rate. Suction lysimeters, installed at seven depths (0.3, 0.6, 1.0, 1.4, 1.8, 2.4, and 3.0 m) and replicated four times, were used to withdraw daily soil solution samples during leaching. Pore water velocities, v, and dispersion coefficients, D, for a one‐dimensional advection‐dispersion model were fit to the resulting concentration vs. time curves by nonlinear least squares. Pore water velocities were slightly greater on average under drip irrigation and were more uniform across the plot (smaller variance) than under flood irrigation. Preferential flow was observed under both irrigation regimes. Breakthrough curves showed considerably more spreading under intermittent flood irrigation than under drip, indicating greater hydrodynamic dispersion under flood irrigation. Fitted D values were, on average, nearly three times greater under flood irrigation than under drip. Allowing free water at the soil surface during flood irrigation increased the dispersion of tracer compared with the drip irrigation system, where water was applied at a rate less than the saturated conductivity. The increase in D is most likely due to small‐scale spatial variability of the soil's hydraulic properties.
Hydraulic Properties of Surface Seals in Georgia Soils
Authors: Chiang S. C. , Radcliffe D. E. , Miller W. P. 
Published: July 2010

AbstractTo predict infiltration in a sealing soil, the seal hydraulic conductivity as a function of time or cumulative rainfall must be known. Few studies have reported measured seal hydraulic conductivities in soils from the southeast USA. Seven Georgia soils packed in columns were subjected to simulated rainfall at an intensity of 50 mm h−1. The sandy loam soils were easily disrupted by rainfall. The calculated seal hydraulic conductivities (Kc) dropped sharply in 10 min of rain and were less than 10% of the initial saturated hydraulic conductivity (Ki) after 45 min. The sandy loam soil with low aggregate stability and Fe content was especially prone to sealing in that Kc dropped to 4% of Ki after 10 min. The well‐structured soil with a clay texture declined in Kc gradually with time, indicating a high resistance to rainfall energy. The sandiest soil showed intermediate resistance to raindrop impact, and Kc leveled off at a high value after 20 min due to the low clay content. The loamy soil with smectitic clay had the lowest Ki and showed little change in Kc with time. Relative seal hydraulic conductivity after 10 or 60 min of rain were good indices differentiating the relative resistance of these soils to surface sealing. A soil stability factor, used to characterize the decrease of Kc in an exponential decay equation, was significantly correlated with water‐dispersible clay on a soil basis.
Reevaluation of the Evaporation Method for Determining Hydraulic Functions in Unsaturated Soils
Authors: Wendroth Ole , Ehlers W. , Hopmans J. W. , Kage H. , Halbertsma J. , Wösten J. H. M. 
Published: July 2010

AbstractUnderstanding of soil water and solute transport processes requires knowledge of the soil hydraulic properties. A simple evaporation method for the determination of the hydraulic conductivity function and the water retention characteristic was developed and applied to a range of soils with different texture and structure. During evaporation from the top of a 6‐cm‐high soil core, soil water pressure head at 1.5 and 4.5 cm below the soil surface was measured with tensiometers several times. At the same time, evaporative water loss was determined by weighing the soil column. The procedure for calculation of hydraulic functions was evaluated via numerical simulations. Results from the numerical experiment confirm the underlying theory. A limitation of the evaporation method is the fact that, at water contents near saturation where hydraulic conductivity is high, hydraulic gradients cannot be determined with sufficient accuracy. Other measurement techniques are suggested that can supplement the evaporation method in the wet range.
Fiberglass Wick Preparation for Use in Passive Capillary Wick Soil Pore‐Water Samplers
Authors: Knutson J. H. , Lee S. B. , Zhang W. Q. , Selker J. S. 
Published: July 2010

AbstractPassive capillary samplers (PCAPS) use the capillary potential generated by hanging fiberglass wicks to exert a sampling suction on soil water. Impurities on the fiberglass affect the capillary properties of the wick and the chemical properties of the samples collected. To determine the need, and a method, for cleaning the wicks, capillary rise and moisture contents were measured using four preparations: uncleaned, detergent washed, acetone extracted, and combusted. Wicks were made with fibers produced by PPG Industries and Manville Company. Results showed that wicks made from PPG fibers lost up to 3.4% of original mass during combustion while Manville fiber wicks lost <0.6%. These losses are assumed to have been due to combustion of organic compounds applied by the manufacturers. All cleaning methods had higher capillary rise than obtained with uncleaned wicks. Combustion at 400 °C for 4 h was the best cleaning method, removing 98 to 100% of impurities.
Horizontal and Vertical Movements of Two Expansive Soils in Mississippi
Authors: Cheng Yaan , Pettry D. E. 
Published: July 2010

AbstractExpansive soils create severe problems for road construction and maintenance, building foundations, and agricultural and industrial operations. Quantification of soil movement under natural field conditions has received little attention and is not well understood. Horizontal and vertical movements were measured for 20 mo by surveying rods placed at various depths in field plots of Typic Chromuderts and Vertic Hapludalfs of the Mississippi Blackland Prairie. Vertical soil movement was a function of soil depth, soil water content, and rainfall. Greatest vertical soil movement occurred in the upper 50 cm of both soils, with a maximum of 27 mm in the Vertisol and 24 mm in the Alfisol. Soil swelling occurred in winter and shrinking occurred in late spring and summer. Horizontal soil movement was not related to soil depth, but was related to soil water content and rainfall. Maximum horizontal movement was 36 mm in the Vertisol and 20 mm in the Alfisol. Horizontal and vertical movements in expansive soils are reversible, dynamic processes under natural field conditions. Horizontal movement appears more dynamic than vertical movement, and it reflects short‐term response to precipitation events followed by drier periods. Vertical movement reflects long‐term precipitation‐evapotranspiration distribution and is probably related to movement along master slickensides.
Foliar Nutrients in Sugar Maple Forests along a Regional Pollution‐Climate Gradient
Authors: Burton Andrew J. , Pregitzer Kurt S. , MacDonald Neil W. 
Published: July 2010

AbstractStressing agents such as defoliation, adverse climatic conditions, and pollutant deposition have the potential to alter forest nutrition. Several recent instances of sugar maple (Acer saccharum Marsh.) decline and dieback have been associated with foliar nutrients deficiencies. This study assessed foliar nutrient status and cycling in five sugar maple dominated northern hardwood forests along a Great Lakes pollution‐climatic gradient. Concentrations and contents in mid‐July foliage and litterfall were determined at each site for N, P, S, Ca, Mg, K, Al, Fe, Mn, B, Zn, and Cu. Where differences existed among sites in foliar nutrient concentrations, they could be predicted primarily from soil properties. Two notable exceptions were foliar S, which was strongly related to SO4 deposition, and foliar Al, which could be predicted by a combination of soil nutrient cation availability and SO4 deposition. Nutrient content of mid‐July foliage and litterfall increased from northwest to southeast along the gradient for N, S, Mg, Al, Fe, B, and Cu. This was the result of an increase in foliage and litterfall biomass, combined in some cases (S, Al, Fe, and B) with increasing foliar nutrient concentrations. Reproductive effort significantly affected total litter return of all nutrients and 43 to 62% of mid‐July foliar N, P, K, and S were conserved through retranslocation prior to litterfall. Sugar maple foliar nutrient concentrations for the five sites revealed no obvious nutrient deficiencies or toxicities, and provide a regional baseline against which the effects of long‐term pollutant deposition and other stresses can be assessed in the future.
Optimal Spacing of Surface‐Banded Nitrogen on Fescue
Authors: Vigil M. F. , Kissel D. E. , Cabrera M. L. , Raczkowski C. W. 
Published: July 2010

AbstractA recommended N application method for approximately 0.2 million ha of tall fescue (Festuca arundinacea Schreb.) grown in Kansas is topdress banding in early spring. Optimal spacing of N fertilizer bands increases N use efficiency, thereby reducing expenditures for fertilizer and the potential for environmental contamination. The objective of this study was to develop and test a model to determine optimal spacing of surface‐banded N from tall fescue dry matter measured on plots fertilized with single bands. A major assumption in the development of the model was: the yield at any point between two fertilizer bands is the sum of yield responses from adjacent bands. In 1985 tall fescue yields measured at various distances from single bands of N fertilizer (applied at rates of 30, 60, 90, and 180 kg ha−1) were used to develop the model. The yields on another set of plots fertilized in a complete factorial arrangement at rates of 60 or 180 kg N ha−1, with band spacings of 25 and 50 cm, were used to test the model in 1984 and 1985. Measured and model‐predicted yields indicated that optimal band spacing was near 25 cm. The model predicted a decrease in optimal band spacing with increasing N rates. The fitted regression of measured yield on predicted yield had a slope and an intercept not significantly different from one and zero, respectively, indicating a good fit between measured and modeled yields. This research provides a practical tool to predict fertilizer band spacings that maximize fescue yields at N rates between 30 and 180 kg N ha−1.
The Distributed Recharge Mechanism in the Australian Arid Zone
Authors: Barnes C. J. , Jacobson G. , Smith G. D. 
Published: July 2010

AbstractWe developed a model to describe fluctuations in historical records of well water levels in the Australian arid zone in order to determine the average recharge rate and specific yield of the phreatic aquifer. The model was used to explore the degree to which variations in solute concentrations are preserved in the deep unsaturated zone during convection to the water table during recharge of rainwater. An examination of historical water levels in wells gives support to the hypothesis (obtained from an earlier study on NO3 contamination of groundwater) that distributed recharge is the primary source of groundwater renewal. Detailed comparison of the hydrograph records suggests a nonlinear response to rainfall, with an “initial loss” of approximately 130 mm mo−1 (five times the mean rainfall). The best estimate of the long‐term recharge rate is about 20 mm yr−1, although the last 10 yr appear to have been somewhat wetter than usual, due mainly to a very large rainfall event in 1989. This recharge mechanism implies that historical environmental tracer signals in recharge waters moving through deep unsaturated zones in unstructured soils will be largely unaffected, when recharge rates are low, by dispersion or even diffusion below a depth that depends on the variability of the rainfall.
Changes in Surface Runoff and Sediment Production after Repeated Rangeland Burns
Authors: Emmerich William E. , Cox Jerry R. 
Published: July 2010

AbstractPrescribed burning of vegetation may increase the potential for surface runoff and erosion. Changes in surface runoff and sediment production were evaluated with time following fall and spring burns at two different soil and vegetation type locations in southeastern Arizona. Rainfall simulations were conducted immediately after prescribed burns on four replicate areas and 1 yr later following a repeat burn on the same areas, and compared with paired unburned areas. The burn treatment and evaluation sequence was repeated in a second year on new areas to evaluate differences in years. After the first burn, runoff and sediment production on unburned and burned areas were similar within locations, and were greater at one location than the other. One location showed significantly more runoff and sediment production in the fall season on both unburned and burned areas after the first burn treatment. There was significantly greater runoff and sediment production from the burned areas after the second burn and the burned areas were now similar between locations. Runoff and sediment production for the fall season and for the second year on the 1‐yr‐old areas was higher at both locations, regardless of treatment. The increases in runoff and sediment production were greater from the burning than the season or year effects after 1 yr. The management implications for these locations and conditions are that, immediately after a rangeland burn, runoff and sediment production maybe unchanged, but within 1 yr significant increases can occur and significant seasonal and yearly differences may occur irrespective of a burn.
Variability in the Growth of Faidherbia albida: The Soils Connection
Authors: Geiger S. C. , Vandenbeldt R. J. , Manu A. 
Published: July 2010

AbstractVariability in the growth of Faidherbia albida (Del.) A. Chev. (syn. Acacia albida [Del.]) in the Sahelian zone of West Africa is a common observation. The “albida effect” has been attributed to the amelioration of soil chemical, physical, and microbiological properties by the direct action of the tree, resulting in enhanced crop production beneath the mature canopy. Crop yields within fields without F. albida can also be highly variable within short distances. A study was conducted to observe the association between the variability in soil properties and the variable growth of young (2‐yr‐old) F. albida trees planted at the ICRISAT Sahelian Center located near Niamey, Niger. The results of this study indicate that the variability in F. albida growth is caused, in large part, by variability in soil properties across relatively short distances. Good growth sites had higher clay contents and base saturations, and lower exchangeable acidity than poor growth sites within the field. The tallest trees in the field were associated with the proximity to abandoned termite mounds and other microhigh sites. Seedlings planted on sheet‐eroded sites caused by runoff from micro‐topographical high sites within the field grew poorly. The variability in F. albida growth in plantations within Niger is hypothesized to be due, in part, to preexisting soil conditions. These results also suggest that the albida effect might be partially caused by these preexisting “islands of fertility”. This site‐determined variable growth of F. albida could be exploited with proper seedling placement strategies.
Statistical and Fractal Evaluation of the Spatial Characteristics of Soil Surface Strength
Authors: Folorunso O. A. , Puente C. E. , Rolston D. E. , Pinzón J. E. 
Published: July 2010

AbstractIn order to understand processes causing soil crusting and to optimize sampling schemes, improved understanding of crust spatial characteristics is needed. For this purpose, statistical and fractal analyses of soil surface strength, as measured by a 1.59‐mm‐diam. flat‐tipped micropenetrometer, were carried out for a variety of soils and under a variety of sampling schemes. Specifically, this work considered maximum penetration forces sampled at intervals of 0.005, 0.01, 0.05 and 0.5 m along four parallel transects 0.25 m apart, for nine different sites within California's Central Valley. Force measurements were non‐homogeneous in space. For eight of the nine sites, both the mean and the variance were non constant; and for all sites, the range and nugget variance of fitted semivariograms were scale dependent. Fractal analysis of the measurements allowed qualitative discrimination among soils, despite small variations across scales. For all sites, fractal dimensions of sampled series at alternative scales were similar, but the smallest deviations across scales were observed on high‐strength silt loam, and the largest on low‐strength loamy sand soils. Multifractal spectra (for data sets normalized and interpreted as probability measures) gave similar entropy dimensions for all sampling schemes, with very small deviations across scales for silt loam soils and largest again for loamy sands. Results suggest that the fractal attributes (fractal and entropy dimensions), being scale‐independent attributes, may be relevant qualifiers of the intrinsic variability of penetration measurements and that this variability can be modeled as a fractal process.
Nondestructive Determination of Hydrogeometrical Characteristics of Soil Macropores
Authors: Wang D. , Norman J. M. , Lowery B. , McSweeney K. 
Published: July 2010

AbstractHydrological and geometrical parameters of macropores are essential for modeling water and solute transport through soils containing macropores. This study was conducted to develop a fast and nondestructive technique for determining the hydrological and geometrical characteristics of soil macropores. We measured the rate of water flowing into ant and earthworm burrows with a macropore infiltrometer and estimated burrow diameter, volume, and depth from the measured flow rate and a water flow model. To evaluate the estimated burrow parameters, we made castings of the ant and earthworm burrows with a dental plaster. The burrows had similar diameters (2.1 mm for laminar flow; 2.9 mm for turbulent flow) but different volumes and depths (281‐cm3 volume and 0.60‐m depth for ant burrows; 210‐cm3 volume and 0.82‐m depth for earthworm burrows). This technique is reasonable for ant burrows because the root mean square difference (RMSD) between casting and infiltrometer‐calculated volumes is 17%; however, errors are larger for earthworm burrows (RMSD is 73%). Saturated soil matrix hydraulic conductivity (Ks) estimated from the infiltrometer measurement of earthworm burrows were comparable to matrix Ks of the bulk silt loam. The matrix Ks values estimated for ant burrows were about eight times smaller than matrix Ks of the bulk sandy soil. Such large decrease in Ks is probably caused by infilling of burrow walls by ants with fine materials. Combining the macropore infiltrometer measurements with the model is a useful means of estimating the hydrological and geometrical parameters of ant and possibly earthworm burrows.
Automatic Atomized Water Spray System for Soil Hydraulic Conductivity Measurements
Authors: Dirksen C. , Matula S. 
Published: July 2010

AbstractSoil hydraulic conductivity, K, as function of volumetric water content, θ, must be known accurately for any quantitative investigation of water and solute transport in unsaturated soil. Direct measurements of K(θ) are hampered by lack of a suitable apparatus to apply small and spatially uniform water flux densities to soil surfaces for extended periods of time. We developed an automatic atomized water spray system that meets these requirements. Results indicate that, with this water spray system, soil hydraulic conductivities between saturation and values approaching 0.1 mm/d can be measured easily, quickly, and accurately. Hydraulic conductivities were a single‐valued function of water content, measured simultaneously with time‐domain reflectometry, but not of pressure head.
Long‐Term Soil Chemistry Changes in Aggrading Forest Ecosystems
Authors: Knoepp Jennifer Donaldson , Swank Wayne T. 
Published: July 2010

AbstractAssessing potential long‐term forest productivity requires identification of the processes regulating chemical changes in forest soils. We resampled the litter layer and upper two mineral soil horizons, A and AB/BA, in two aggrading southern Appalachian watersheds 20 yr after an earlier sampling. Soils from a mixed‐hardwood watershed exhibited a small but significant decrease in soil pH. Extractable base cation content declined substantially in both mineral horizons. For example, Ca2+ levels in the A horizon fell from 236 kg ha−1 in 1970 to 80 kg ha−1 in 1990. Proportionally, the decline was greatest for Mg2+, which dropped from 111 to 20 kg ha−1. A white pine (Pinus strobus L.) plantation was planted in 1956, after clear‐felling hardwoods and recutting sprouts for 15 yr. Soil pH and base cation concentrations declined in the A horizon from 1970 to 1990. Soil pH declined from 5.9 to 5.0 and Ca2+ levels from 534 to 288 kg ha−1. Cation content did not change significantly in the AB/BA soil horizon. Nutrient budgets were constructed using these soil and litter data plus existing data on weathering rates, forest productivity, and hydrologic fluxes and associated chemistry. Decreases in soil base cations and soil pH are attributed to leaching and to the sequestration of nutrients in biomass.