bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐Term Swine Lagoon Effluent Applications on ‘Coastal’ Bermudagrass: I. Yield, Quality, and Element Removal
Authors: Burns J. C. , King L. D. , Westerman P. W.
Published: July 2010

Swine (Sus scrofa domesticus) confinement systems that use anaerobic lagoons for waste collection in the humid regions require effluent removal during the year. Land area adjacent to the hog facility frequently becomes the site for continuous effluent distribution. The objective of this experiment was to determine the effect of long‐term application of swine lagoon effluent to ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] on dry matter yield, stand persistence, and nutrient concentration and removal. Effluent loading rates of low (L), medium (M), and high (H) approximating 335, 670, and 1340 kg of N ha−1 yr−1, respectively, were evaluated for 11 yr beginning in 1973 through 1983. The experiment was a randomized complete block with three replicates. Dry matter yields in Year 11 were altered by effluent loading rates with greater production from the M (19.0 Mg ha−1) or H (19.6 Mg ha−1) compared with the L (13.1 Mg ha−1). Although fluxes in stands occurred, they recovered completely as indicated by these yields. Higher concentrations of N, P, K, Mg, Cl, and Zn were present in forage in 1983 compared with 1973. Calcium was unchanged and Cu, Fe, and Na were less. In vitro dry matter disappearance of the forage was similar among loading rates (0.634) in 1983 and greater than in 1973 (0.553). Concentrations of NO3‐N were higher in 1978 (1.14 g kg−1) compared with 1973 (0.87 g kg−1), but highest concentrations occurred in 1983 (1.57 g kg−1). By 1983, NO3‐N concentrations of forages from the H loading rate approached or exceeded the toxic threshold in all summer harvests. Only the H loading (1340 kg ha−1) caused unstable stands and eventually produced forage that had NO3‐N concentrations potentially toxic if fed as the sole ration to ruminants. Further, it resulted in disproportionally greater quantities of elements—especially N, P, K, Cl, and Na—that remained in the soil environment to become potential soil and soil‐water pollutants.
The Effect of Deicing Salts on Trace Metal Mobility in Roadside Soils
Authors: Amrhein Christopher , Strong James E.
Published: July 2010

Calcium magnesium acetate (CMA) (Ca0.3Mg0.7(C2H3O2)2) is being used as an alternative to NaCl for deicing highways. CMA is an effective deicer, handles well, biodegrades, is less toxic to aquatic life, and is less corrosive than Cl salts. There is some concern, however, that CMA may increase the mobility of certain trace metals from roadside soils. Roadside soils were collected from around the USA from high‐traffic and high‐salt use areas. These soils were characterized for total trace metal content as well as important chemical and physical parameters. Studies were carried out to determine (i) the effect of CMA decomposition on Pb and Cd concentrations in an aqueous system (no soil), (ii) changes in major and minor element chemistry in soils incubated with NaCl and CMA solutions, and (iii) the mobility of trace metals from soil columns leached with solutions of deicing chemicals and/or H2O. Microbial decomposition of the acetate resulted in increased pH, CaCO3 precipitation, and immobilization of Cd either through coprecipitation with CaCO3 or CdCO3 precipitation. There was no difference in trace metal solubility in soils treated with H2O or 10 mmolc L−1 CMA or NaCl (average runoff concentration). Trace metal concentrations were initially high in soils treated with 100 mmolc L−1 solutions of deicing salts but concentrations decreased with time due to adsorption or precipitation reactions. The leachability of Pb from soil columns was strongly correlated with organic matter solubilization. Soils leached with NaCl followed by distilled water had reduced permeabilities as compared to CMA‐leached soils. It appears the effect of CMA on trace metal mobility in roadside soils should generally be beneficial.
Salinity, Nitrate, and Water in Rangeland and Terraced Wheatland above Saline Seeps
Authors: Berg W. A. , Naney J. W. , Smith S. J.
Published: July 2010

Saline seeps have emerged over the past 20 yr in some Southern Plains soils cropped annually to winter wheat (Triticum aestivum L.). Saline seep development is a cumulative process associated with percolation of small increments of water over many years through saline strata in recharge areas to build up water tables over less‐permeable strata in lower slope positions. In this study soluble salt, nitrate, and water content were determined in Woodward soils (coarse silty, mixed, thermic Typic Ustochrepts) to a depth of 3 in terraced farmland and in adjacent native rangeland upslope from saline seeps. Significantly (P<0.05) more soluble salt was present in the surface 3 m of rangeland than in adjacent farmland. No difference (P>0.05) was found in soluble salt content in farmland between terraces as compared to soluble salt in terrace channels. Greater amounts (P<0.05) of nitrate and water were in the 3‐m profiles under farmland than under native range. The soluble salt profiles indicate more water has percolated through the farmland than the rangeland. The implication is cultivated land, both in terrace channels and between terraces, is contributing salt and water to saline seep. An alternative explanation is terrace channels are the major recharge areas and lateral flow of this water leachesalt from farmland between the terraces.
Maize Production Impacts on Groundwater Quality
Authors: Schepers J. S. , Moravek M. G. , Alberts E. E. , Frank K. D.
Published: July 2010

The cumulative effects of management practices on nitrate‐nitrogen (NO3‐N) leaching and groundwater quality are frequently difficult to document because of the time required for expression and the diversity of interacting processes involved. This work reports results of a N and water management program initiated by the Central Platte Natural Resource District (CPNRD) in Nebraska. Cultural practices recommended by the CPNRD and reported by producers for the 1988 growing season, representing approximately 3900 fields covering 84 210 ha of irrigated corn (Zea mays L.) indicated NO3‐N contamination of groundwater was influenced by yield goals and fertilizer N application rates. Groundwater NO3‐N concentrations were positively correlated with residual N in the surface 0.9 m of soil prior to the growing season, reflecting the effects of past N and water management practices. Yield goals in 1988 averaged 9% higher than the average 10.0 Mg ha−1 corn yield attained, which accounts for an average of about 20 kg N ha−1 in excess of the average N recommendation. By comparison, in a 1980 to 1984 study from an area within the CPNRD, yield goals averaged 28% greater than actual yields. Overly optimistic yield goals in 1988 accounted for 42% of the average excess N application rate of 48 kg ha−1 (based on University of Nebraska recommendations). A large portion of average excess N application is attributed to producers in 14% of the area who applied >100 kg N ha−1 more than the recommended rates. Fertilizer N applied showed little relationship to fertilizer N recommended. Better education and more stringent measures may be required to address the select group of producers who fail to follow CPNRD recommendations.
Effects of Spatial Accumulation of Runoff on Watershed Response
Authors: Garbrecht Jurgen
Published: July 2010

The drainage network accumulates upstream subwatershed runoff into a single downstream response, with runoff accumulating at network junctions. The effects of this accumulation on the magnitude and spatial variability of the downstream response are reviewed for simplified boundary conditions. Runoff parameters are runoff depth and corresponding unit area peak runoff rate. At the subwatershed level these parameters are referred to as d and q, respectively, and they vary from one subwatershed to another. At a downstream location, after accumulation by the drainage network, corresponding parameters are referred to as D and Q. Equations expressing the effects of runoff accumulation are formulated and discussed for uniform rainfall conditions. The review shows that the effects of runoff accumulation gain in importance as the number of upstream subwatersheds and the size of the watershed increase in the downstream direction. The accumulation process cancels extreme values of d and q to yield a representative D and Q value for the entire upstream drainage area. The impact of individual d and q values on the downstream D and Q values in the channel diminishes as the number of upstream subwatersheds increases. This results in a decrease in the spatial variability of D and Q in the downstream direction. The review suggests that the role of spatial variability of upstream d and q in the determination of downstream D and Q diminishes as watershed size increases. However, nonuniform rainfall distributions and storm movement may overshadow the effects of runoff accumulation when watershed size increases beyond the size of the storm.
Modeling the Cumulative Watershed Effects of Forest Management Strategies
Authors: Ziemer R. R. , Lewis J. , Rice R. M. , Lisle T. E.
Published: July 2010

There is increasing concern over the possibility of adverse cumulative watershed effects from intensive forest management. It is impractical to address many aspects of the problem experimentally because to do so would require studying large watersheds for 100 yr or more. One such aspect is the long‐term effect of forest management strategies on erosion and sedimentation and the resultant damage to fish habitat. Is dispersing activities in time and space an effective way to minimize cumulative sedimentation effects? To address this problem, Monte Carlo simulations were conducted on four hypothetical 10 000‐ha fifth‐order forested watersheds: one watershed was left undisturbed, one was completely clearcut and roaded in 10 yr, with cutting starting at the head of the watershed and progressing toward the mouth, another was cut at the rate of 1% each year beginning at the watershed's mouth and progressing upstream, and another was cut at a rate of 1% each year, with individual cut areas being widely dispersed throughout the watershed. These cutting patterns were repeated in succeeding centuries, rebuilding one‐third of the road network every 100 yr. The parameters governing the simulations were based on recent data from coastal Oregon and northwestern California. Mass wasting, the most important source of sediment in that environment, was the only hillslope process modeled. The simulation results suggest that (i) the greatest differences between management strategies appeared in the first 100 yr and were related primarily to the rate of treatment. By the second 100 yr, when all watersheds had been treated, the principal difference between logging strategies was the timing of impacts. (ii) Dispersing harvest units did not significantly reduce cumulative effects. (iii) The frequency of bed elevation changes between 1 and 4 cm is dramatically increased by logging.
Probability of Sediment Yields from Surface Erosion on Granitic Roadfills in Idaho
Authors: Megahan Walter F. , Monsen Stephen B. , Wilson Monte D.
Published: July 2010

A series of 29 bordered plots, 1.8 m wide by 4.6 m long, was used to measure sediment yields from granitic roadfills on forest roads in the mountains of Idaho. Slope gradients on the plots ranged from 34 to 41°. Sediment yield data for the snowfree season were collected for 3 yr following road construction. Various site factors were tested by regression analysis for their effects on sediment yield, but only ground cover density and snowfree period rainfall erosivity were statistically significant. Analysis of 22 yr of snowfree period rainfall erosivity data showed that erosivity was log‐normally distributed and established the parameters for the probability density function. These data, coupled with the prediction equation from the regression model, were then used in a Monte Carlo simulation model to define the probability of occurrence of sediment yields from granitic roadfills given various levels of ground cover density. Recently published studies that update the slope gradient and slope length components of the Universal Soil Loss Equation are used to extrapolate the results of the present study to all lengths and gradients of granitic roadfills. A discussion of the application of the study results is presented.
A Four‐Year Mobility Study of Selected Trace Elements and Heavy Metals
Authors: Sheppard Marsha I. , Thibault D. H.
Published: July 2010

The environmental impact of accidental or chronic releases of contaminants to the unsaturated soil zone, either through surface spills or contaminated groundwater, has become a major concern. This study was designed to provide data after 1 and 4 yr to compare the leaching and upward transport of Tc, I, Np, Cs, U, Th, Cr, and Mo in cores of the same soil in outdoor lysimeters. Over the 4‐yr study a broad range of climatic, soil moisture, and temperature conditions existed, which were representative of long‐term means as well as some extremes. The amount of rainfall leached through the cores decreased with time. The leaching resulted in a downward movement of fine soil particles, especially in the lower horizons. Element mobility in the leaching cores for the 4 yr decreased in the order I > Tc ≫ Cr > Np > Mo > Cs ≥ U > Th. This differs slightly from the ranking predicted after 1 yr. After 1 yr, Mo appeared to be more mobile than Cr or Np. After 4 yr, I, Tc, Np, and Cs migrated to the soil surface from depth. Analysis of the soil solid/liquid partition coefficient, Kd, values indicates the retention of these elements is primarily related to soil organic matter content and dependent on porewater concentration. The Kd model is appropriate for I in all soil horizons and for Tc, Np, and Cs in the Ae horizon of the groundwater cores. The Freundlich isotherm or a kinetic expression best describes the sorption for all other elements and horizons.
Mathematical Model of Plant Uptake and Translocation of Organic Chemicals: Development of the Model
Authors: Lindstrom F. T. , Boersma L. , McFarlane C.
Published: July 2010

Uptake, translocation, and accumulation of organic chemicals by plants are influenced by plant characteristics, chemical properties, and environmental conditions. Experimental evaluation of plant contamination for the many xenobiotic chemicals now in use or being developed is impractical. A mathematical model was formulated which, when adequately tested, can be used to provide information about potential contamination. The model was formulated by defining a generic plant as a set of adjacent compartments representing the major pools involved in transport and accumulation of water and solutes. The model plant is divided into root, stem, and leaves and each is subdivided into two transport compartments (xylem and phloem) and a storage compartment. Chemical uptake is modeled from the soil solution to the root surface, through the apparent free space, endodermis into the xylem and throughout the plant. Values for the anatomical dimensions of the compartments and for physical and chemical coefficients were chosen from the literature. This article shows formulation of the mass balance equations, which lead to the complete system of equations that describe uptake. The solution gives chemical mass in each compartment as a function of time. The mathematical development yielded a well‐defined concept of uptake, in‐plant transport, and local accumulation of organic chemicals by plants.
Mathematical Model of Plant Uptake and Translocations of Organic Chemicals: Application to Experiments
Authors: Boersma L. , McFarlane C. , Lindstrom F. T.
Published: July 2010

A mathematical model for uptake of organic chemicals by plants was calibrated by application to data from experiments in which the uptake of bromacil (C6H13BrN2O2) by soybean [Glycine max (L.) Merr.] plants was measured. The plants had been exposed to a range of bromacil concentrations at several transpiration rates. The model was initially formulated by defining a generic plant as a set of adjacent compartments representing the major pools and pathways involved in transport and accumulation of water and solutes. For this application the plant consists of one root, three stem, and three leaf compartments, with each compartment being subdivided into xylem, phloem, and storage. The model was calibrated with respect to storage coefficients that quantify rate of transport to and from storage. For calibration, bromacii concentrations measured in roots, stems, and leaves were compared with model predictions, while model parameters were changed until no further improvement in matching model prediction with experiment result was obtained. This calibration exercise revealed important plant behavior demonstrating the value of the model for elucidating plant response. The model was changed during the calibration to account for specific phenomena that occur in the roots and leaves. The information obtained was applied to results from additional experiments. Storage coefficients differed substantially between roots, stems, and leaves showing differences in plant structures and physiological functions. The coefficients generally were proportional to compartment size, independent of transpiration rate except at low concentrations and independent of concentration except at high concentrations. The model satisfactorily predicted the observed uptake and distribution patterns for bromacil in soybean plants at the stage of growth and under the environmental conditions of the experiments.
Changes in Foliar Concentration of Abscisic Acid in Soybean in Response to Sulfur Dioxide Fumigation
Authors: Gupta Gian , Sandhu Ravinder , Mulchi Charles
Published: July 2010

Soybean [Glycine max (L.) Merr.] cv. Elf plants were exposed to 0.0, 0.05, 0.2, and 0.4 µmol mol−1 SO2 in a controlled environment. The amount of abscisic acid (ABA) was measured, using an enzyme linked immunosorbent assay (ELISA), after 1, 2, or 4 h of exposure as well as after 18 h of recovery period. With 0.05 µmol mol−1 SO2, the ABA concentrations in soybean leaves were 28 and 141% higher than the control, with 1 and 4 h exposures, respectively; after an 18‐h recovery period, the ABA concentrations were still higher (23.6 and 42.8% for the 1 and 4 h exposures, respectively). Abscisic acid concentration increased in soybean leaves both with an increase in the concentration of SO2 and the time of exposure.
Foliar Absorption of Atmospheric Ammonia by Ryegrass in the Field
Authors: Sommer S. G. , Jensen E. S.
Published: July 2010

The dry deposition of ammonia (NH3) in the field was measured simultaneously at increasing distances from a point source (a dairy farm) using a biomonitor. The biomonitor was Italian ryegrass (Lolium multiflorum Lam) grown in pots and supplied with 15N‐labeled N. The use of 15N improved the precision and lowered the detection limit of the method compared with calculating the NH3 deposition using the difference method (N‐balance method). Atmospheric NH3‐concentrations were measured by drawing air through traps containing sulfuric acid. At the end of a 6‐wk period in the growing season, the deposition of N was 3.0 g N/m2 and 0.7 g N/m2 at average atmospheric concentrations of 89 and 6 µg NH3‐N/m3, respectively. Estimated deposition velocities ranged from 0.7 to 3.4 cm/s with an average of 1.6 cm/s (s.d. 1.2 cm/s).
Concentration‐Dependent Effects of Ozone on Translocation of Assimilates in Douglas Fir
Authors: Gorissen A. , Schelling G.C. , van Veen J.A.
Published: July 2010

The assessment of air quality standards for forest ecosystems requires proper knowledge about concentration‐effect relations of air pollutants for tree species. In this study, 2‐yr‐old Douglas fir seedlings [Pseudotsuga menziesii (Mirb.) Franco] were exposed to 23, 81, and 169 µg O3/m3 during 8 h/d, 5 d/wk for a period of 4 wk. After exposure, the trees were placed in an atmosphere containing 14CO2. Release of 14CO2 in the root/soil compartment was analyzed once a day and was regarded as an index of transport and utilization of 14C photosynthates. Respiratory release of 14C was temporarily inhibited by O3 during the first days following exposure to the air pollutant. Within 2 wk after the O3 treatment, 14CO2 in the root/soil respiration was the same in all treatments, indicating that trees were recovering from O3 injury.
Mechanisms for Trichloroethylene Vapor Sorption onto Soil Minerals
Authors: Ong Say Kee , Lion Leonard W.
Published: July 2010

Partition coefficients were determined for trichloroethylene (TCE) vapor (P/Po <2% or concentration <10 mg L−1) for several minerals over a wide range of moisture contents. For oven‐dried minerals, surface area was found to be a good indicator of the sorptive capacity of the solid phase. As moisture content was increased, the partition coefficients of TCE vapor decreased by several orders of magnitude, attained a minimum, and then gradually increased. Mechanisms of TCE vapor sorption were proposed corresponding to three regions of sorbent moisture content. In Region 1, from oven‐dried conditions to one monolayer coverage of water on the solid surface, direct solid‐vapor sorption was evident with strong competition between water and TCE for adsorption sites on the sorbents. In Region 2, between a monolayer coverage to approximately five layers of water molecules, likely interactions between TCE vapor and water include sorption of TCE onto surface‐bound water and limited TCE dissolution into sorbed water with some “salting out” effects caused by water structure. In Region 3, extending from a minimum of approximately five layers of water molecules to the water retention capacity of the soil, TCE dissolution into condensed water‐dominated vapor uptake along with sorption at the water solid interface. Thermodynamic data and the development of a simple model were used to interpret the above processes. Application of Henry's Law to model TCE interaction with the soil water was possible only after five layers of water molecules have formed.
Pesticide Mobility and Persistence in Microlysimeter Soil Columns from a Tilled and No‐Tilled Plot
Authors: Fermanich K. J. , Daniel T. C.
Published: July 2010

Pesticide leaching losses under varying tillage systems, especially in sandy soils, is not clearly understood. This study compared the leaching and dissipation of two corn (Zea mays L.), 14C‐labeIed, insecticides—carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzo‐furanylmethylcarbamate) and chlorpyrifos [O,O‐diethly O‐(trichloro‐2‐pyridyl) phosphorothioate]—in sandy soil columns from conventional‐moldboard plow (CN) and no‐till (NT) tillage plots. Microlysimeters, utilizing intact soil columns from established tillage plots, were used to investigate pesticide mobility and dissipation under simulated field precipitation, drainage, and temperature patterns. Leachate from CN tillage columns receiving 14C‐carbofuran contained over two times more of the applied 14C (17.9%) compared to NT columns (7.9%). The major portion (63%) of 14C‐carbofuran residues leached from CN columns was associated with a metabolite (unknown I) compared to 40% for NT columns. Slightly more (4.9% compared to 4.6%) 14C as parent carbofuran leached from CN columns relative to NT. After 106 d of simulated field conditions, 4.0 and 7.8% of the applied parent 14C‐carbofuran was recovered from the soil of CN and NT columns, respectively. Average time to peak 14C‐carbofuran residue concentrations were retarded by 12 and 39 d for CN and NT columns, respectively, compared to time to peak concentrations of bromide. Less than 0.2% of the applied 14C‐chlorpyrifos leached from the soil columns. Differences in the physical, chemical, and/or biological characteristics between CN and NT tillage columns influenced the dissipation and mobility of carbofuran.
Field Decay of Wheat Straw and its Effects on Metribuzin and S‐Ethyl Metribuzin Sorption and Elution from Crop Residues
Authors: Dao Thanh H.
Published: July 2010

Best agricultural management practices (BMP) are needed for minimizing the potential off‐site transport of agricultural chemicals while retaining their chemical efficacy. Field and laboratory studies of herbicide‐crop residue interactions in conservation tillage systems were conducted to determine weather‐induced changes in wheat (Triticum aestivum L.) straw chemical composition, the capacity of plant residues to retain metribuzin [4‐amino‐6‐(1,1dimethyl‐ethyl)‐3‐(methyl‐thio)‐1,2,4‐triazin‐5(4H)‐one] and its S‐ethyl analog (S‐ethyl metribuzin), and the changes in herbicide sorption characteristics of these residues as they decay in the field. At harvest, undecayed wheat straw exhibited Freundlich straw‐water partition coefficients of 13.1 and 24.2 µmol kg−1/(µmol L−1)1/n, where 1/n = 0.78 and 0.60 at 20 °C for metribuzin and S‐ethyl metribuzin, respectively. Lignin accounted for the majority of the sorption capacity of intact wheat straw. The purified cellulose fraction did not significantly sorb the herbicides. Increased sorption capacity of decaying straw was associated with a decline in cellulose concentration or conversely the lignin enrichment of the straw. Field decay reduced straw cellulose concentration at the rate of 1.56 × 10−3 d−1 for straw in partial contact with the ground, following grain harvest in 1983, and 3.97 × 10−4, and 4.39 × 10−4 d−1 for standing straw in 1985, and 1986, respectively. Observed asymmetrical breakthrough curves of both chemicals from packed straw columns also suggested a slow mechanism of release of the herbicides from crop residues. Wheat straw's affinity could reduce herbicidal efficacy of soil‐activated chemicals if they were applied as a surface spray in conservation tillage systems. Although metribuzin and S‐ethyl metribuzin are primarily soil‐activated herbicides, they would still be effective for post‐emergence control of Bromus spp. in winter wheat due to foliar absorption and slow release from the straw mulch. By the same token, the straw mulch is a temporary storage medium to alter these herbicides' environmental dispersion pattern and may be a significant mechanism of retardation of agricultural chemical movement to the subsurface of lands under conservation tillage.
Water Quality Impacts Associated with Wheat Culture in the Southern Plains
Authors: Smith S. J. , Sharpley A. N. , Naney J. W. , Berg W. A. , Jones O. R.
Published: July 2010

Water quality information regarding wheat culture in the Southern Plains is sparse. The objective of this study is to determine the extent to which the area's surface and ground‐water quality is influenced by different wheat cultural practices. Concentrations and amounts of sediment, N and P in surface runoff water were determined for conventional till (CT), reduced till (RT), and no till (NT) wheat (Triticum aestivum L.) watersheds in the High Plain, Reddish Prairie, and Rolling Red Plain land resource areas of Oklahoma and Texas. During the 4 to 6 yr study periods, RT and NT practices were superior to CT for reducing sediment and associated particulate nutrient discharge. Mean annual discharge ranged from 230 to 15 900 kg ha−1 for sediment, 1 to 27 kg ha−1 for total N, and 0.1 to 6 kg ha−1 for total P. Irrespective of tillage practice, annual soluble nutrient losses in surface runoff water tended to be small, often < 1 kg ha−1 N or P. Successful prediction of soluble P, particulate P, and particulate N losses was achieved using appropriate kinetic desorption and enrichment ratio procedures. Soluble N in runoff posed no particular water quality problem, but recommended P levels were exceeded, even from baseline, unfertilized grassland watersheds. With regard to groundwater quality, elevated levels of NO−3 (e.g., 34 mg N L−1 maximum) were observed on one Reddish Prairie NT watershed.
Relations among NaOH‐Extractable Phosphorus, Suspended Solids, and Ortho‐Phosphorus in Streams of Wyoming
Authors: Parker Michael
Published: July 2010

During 1984–1986, 369 water samples from seven streams and a sewage treatment plant in Wyoming were analyzed for NaOH‐extractable P (NaOH‐P; a possible index of biologically available P), ortho‐P (OP), and suspended solids (SS). Regressions predicting NaOH‐P were developed from data on SS and OP, plus information on variability in time (year of sampling), meteorology (volume discharge), and presence/absence of beaver (Castor sp.) dams. Scatter plots, ANOVA, and cluster analyses indicated data could be aggregated into four groups reflecting processes that differ among the eight stations (e.g., relations among volume discharge, SS, and OP). These groups are composed of one to three stations, and index a component of spatial variability. Adjusted R2 and precision (95% confidence limits for the mean) always tended to be poor when OP was more influential in affecting NaOH‐P than were SS (R2 = 21–88%); only in some cases where SS were highly influential were adjusted R2 and precision good. If data presented are representative, then the best precision obtainable from regressions will be about ±50% of the mean value for NaOH‐P. This value compares favorably with many other techniques, so predicting NaOH‐P from regressions should be useful for some applications.
Measurement and Characterization of Macropores by using AUTOCAD and Automatic Image Analysis
Authors: Singh Piyush , Kanwar Rameshwar S. , Thompson Michael L.
Published: July 2010

Macropores (with equivalent diameters greater than 1600 µm) were quantified under no‐till and conventional tillage practices by using AUTOCAD and automatic image analysis. To quantify macropores, undisturbed soil blocks (50 by 50 cm) were impregnated with plaster of paris slurry. After the plaster of paris set, soil layers were taken out in 5‐cm increments to a total depth of 60 cm. At each soil plane pictures were taken by a 35‐mm camera and macropores were traced on transparent acetate sheets. The pictures and transparent sheets were analyzed by using an automated image analyzer and AUTOCAD, respectively, for total number, perimeter, area, and size frequency distribution of macropores. The AUTOCAD method proved to be simpler and better than the image analysis technique. Larger and continuous cracks accounted for greater macropore area in conventional tillage sites than in no‐till sites. On the other hand, more worm holes and root holes accounted for a greater number and larger perimeters of macropores in no‐till sites in comparison to conventional tillage sites.
Positional, Spatially Correlated and Random Components of Variability in Carbon Dioxide Efllux
Authors: Aiken R. M. , Jawson M. D. , Grahammer K. , Polymenopoulos A. D.
Published: July 2010

The ability to distinguish spatial variability either from deterministic trends or from experimental treatment effects contributes to the accuracy and interpretation of field experiments. The objective of this study was to characterize three components of soil and soil plus vegetation CO2 efllux: the positional trend, spatial correlation, and random variation. Soil CO2 efflux was measured in a wheat (Triticum aestivum L.) field at two different dates with differing soil water contents, and soil plus vegetative CO2 efflux was measured at three grassland sites. Carbon dioxide efflux was determined by the alkali absorption method using static chambers located at 3‐m intervals within a 18 m by 18 m square grid. Positional trends were identified using a multiple regression technique, and with a t‐test extended into two dimensions. Data were detrended using a generalized least squares (GLS) regression procedure. Semivariograms were used for analysis of spatial correlation and random variability. The assumption of spatial homogeneity (first‐order stationarity) was not founded for CO2 efflux for four of the five data sets. Positional trends accounted for 16 to 48% of the total variability in these cases. Spatial correlation was not detected, although ignoring positional trends may well have resulted in the opposite conclusion. Spatial structure was affected by the soil water content under wheat. Defining the spatial structure of soil respiration requires determinations under a range of environmental conditions. Advantages of the trend identification and quantification procedures utilized are direct application of common regression techniques, direct evaluation of first‐order stationarity following trend removal and correction for correlated error structure.
Propanil: Toxicological Characteristics, Metabolism, and Biodegradation Potential in Soil
Authors: Pothuluri Jairaj V. , Hinson Jack A. , Cerniglia Carl E.
Published: July 2010

Propanil [3′,4′‐dichloropropionanilide (DCPA)] is a biologically active pollutant. Propanil is extensively used around the world for control of weeds in rice (Oryza sativa L.) production. Although propunil by itself is of low toxicity, the highly toxic impurities 3,3′,4,4′‐tetrachloroazobenzene (TCAB) and 3,3′,4,4′‐tetrachloroazoxybenzene (TCAOB) from the manufacture of 3,4‐dichloroaniline (DCA) often contaminate the 3,4‐DCA‐derived herbicide propanil. These componnds are approximately isosteric to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD), and acting at the Ah receptor, are toxic by mechanisms similar to those of TCDD. Both TCAB and TCAOB are cytotoxic, embryolethal, and teratogenic, and hence are classified as possible human genotoxins. In soil, biodegradation of propanil liberates DCA, which is converted by microbial peroxidases to TCAB and other azo products. The TCAB and TCAOB may accumulate in rice‐growing soils, and leach into groundwater. The toxicity and fate of these compounds in the environment and the ability of microorganisms to detoxify them are discussed.
An Evaluation of Nitrogen Mineralization Indices for Organic Residues
Authors: Douglas B.F. , Magdoff F.R.
Published: July 2010

Organic residues without high levels of toxic metal or organic constituents are usually applied to agricultural soils at rates based on assumed contributions of available N to the growing crop. However, there is no accepted test for assessing potential available N supply from residues. Although the actual contribution will depend on soil characteristics and climate as well as residue characteristics, a chemical index might be useful in ranking residues according to potential available N contributions. An experiment was conducted to evaluate a number of chemical indices for N availability. The 19 residues used in the study consisted of seven types of manures, six sewage sludges, and six composted or mixed soil amendments. Organic residues were mixed with sandy top‐soil and perlite and incubated in glass tubes in the laboratory for 67 d. Total N, total Kjeldahl N, organic N, and N released into the Walkely‐Black acid‐dichromate digest (WBN) were significantly correlated with the amount of N mineralized as well as the fraction of organic N mineralized during the incubation. The best relationship for the amount of N mineralized was with WBN (r2 = 0.89 for a quadratic relationship). The strongest of the correlations for fraction of organic N mineralized was also with WBN (r2 = 0.82).
Transport and Prediction of Sulfate in Agricultural Runoff
Authors: Sharpley Andrew N. , Smith S. J. , Jones O. R. , Berg W. A. , Coleman G. A.
Published: July 2010

The measurement and simulation of sulfate‐S (SO4‐S) mobility in agricultural watersheds is necessary to evaluate the effect of management practices on associated crop S deficiencies, enhanced leaching loss of nutrient cations, and acidification of percolation waters. The concentrations and amounts of SO4‐S in runoff from six grassed and 13 cropped watersheds in the Southern Plains were, thus, measared over a 4‐yr period. Sulfate‐S transport in runoff was predicted using an equation describing the kinetics of SO4‐S desorption from soil and compared with measured values. No SO4‐S was added to any of the watersheds directly as S fertilizer or indirectly in N or P fertilizer material. No difference (at 5% level) in SO4‐S concentration in runoff from grassed (mean annual value of 12.6 mg L−1) and cropped (mean annual value of 11.0 mg L−1) watersheds was observed. Differences in amounts (0.2–18.9 kg ha−1 yr−1) were a function of runoff volume as influenced by land management. A general trend of increasing SO4‐S concentration in runoff with decreasing pH was observed, which may be a function of S dry deposition and soil and crop conditions. Measured and predicted SO4‐S concentrations in runoff for individual events were not significantly different (at 5% level), with an average predictive standard error of 1.6 mg L−1 for all watersheds, representing 17% of the measured concentration. The equation may, thus, provide a predictive tool in agronomic and environmental studies of SO4‐S movement in agricultural watersheds.
Chemical Composition of Ochreous Precipitates from Ohio Coal Mine Drainage
Authors: Winland R. L. , Traina S. J. , Bigham J. M.
Published: July 2010

Ochreous precipitates and associated solutions were collected from waters draining abandoned coal works at 28 locations in eastern Ohio. Major and trace element contents of the precipitates were determined, and comparisons were made with source solutions to evaluate the effects of pH, organic C, and ionic strength on solid‐phase composition and trace metal distribution. The pH and calcalated ionic strength of the effluents ranged from 2.6 to 7.8 and 6 to 106 mmol L−1, respectively. Associated precipitates consisted primarily of poorly crystallized oxides and oxyhydroxides of Fe with jarosite occuring as a major constituent of only one specimen. Mean Fe, SO4, Al, and Si contents of the precipitates were 8.7, 1.34, 1.11, and 0.25 tool kg−1, respectively. Silicon content increased with increasing pH of the source solution suggesting pH‐dependent adsorption. In contrast, SO4 and Al appeared to be influenced both by precipitation and adsorption reactions. Partition coefficients for As, B, Ba, Co, Cu, Cr, Mn, P, and Zn showed a preferential accumulation of all elements by the solid phase with mean log Kd values ranging from 2.9 for Cu to 6.3 for As. Manganese, Co, and Zn all showed increased partitioning into the solid phase with increasing pH and decreasing ionic strength of the drainage waters. Copper appeared to be strongly associated with organic matter, and a weaker but positive relationship was also observed with Co and Zn. No effects of pH, ionic strength, or organic C were observed for any other trace elements. Solubility equilibrium calculations suggested that the solid phase concentrations of Co, Cr, Cu, Mn, Zn, and As were primarily controlled by adsorption and/or coprecipitation phenomena whereas Ba and P activities in solution exceeded the solubilities of barite and strengite, respectively.
A Branch Exposure Chamber for Fumigating Ponderosa Pine to Atmospheric Pollution
Authors: Houpis James L. J. , Costella Mark P. , Cowles S.
Published: July 2010

The investigation of the effects of atmospheric pollution on metabolism and growth of woody species has long been hampered by the very difficult task of exposing mature individuals to controlled environments of air pollutants. This paper describes the design, construction, and testing of an alternative tool to whole‐tree enclosures for measuring pollution response in mature woody tissue. The chamber is a new design, though not a new concept, and is referred to as a branch exposure chamber. Designed primarily for ozone and acid precipitation exposures (and used additionally for CO2 measurements), the branch exposure chamber incorporates four major parts: support structure, fan‐air supply unit, charcoal filter unit, and exposure chamber. The exposure chamber is a 1.5‐m long by 0.7‐m diam. cylinder. The chamber is constructed of Teflon sheeting stretched over an aluminum frame; the aluminum frame is totally wrapped with nonreactive, aluminum‐backed Teflon tape. Three zones in the chamber affect exposure of the experimental tissue: an initial buffer region for mixing, a main exposure region, and an exhaust frustrum. Aerodynamic testing of the chamber‐mixing characteristics show that mixing is uniform and complete within the main exposure region. Thermal buildup within the chamber was a maximum of 3 °C under a wide range of ambient meteorological conditions. Based on current field trials of the chamber, material deterioration due to environmental variables (e.g., ultraviolet radiation, heat oxidants), is not expected to affect operation of the chamber for 24 mo. The BEC is inexpensive to build and operate, and represents a viable alternative to a whole‐tree chamber.
Trough Versus Funnel Collectors for Measuring Throughfall Volumes
Authors: Reynolds B. , Neal C.
Published: July 2010

Throughfall was collected, at fortnightly intervals, for 1 yr beneath mature stands of Sitka spruce [Picea sitchensis (Bong.) Carr.] and Japanese larch [Larix kaempferi (Lamb.) Carr.] using arrays of troughs and funnels. There was no statistically significant difference between the annual total amounts of throughfall collected by the troughs and the funnels. Analysis of the fortnightly data revealed a small bias toward a lower catch by the troughs, although for any given fortnight, quite large differences might occur. Discussion of the results in relation to a recent paper by Kostelnik et al. concludes that there is insufficient evidence on which to reject funnels in favor of troughs for throughfall studies.
Runoff and Sediment Losses from Tall Fescue under Simulated Rainfall
Authors: Gross C. M. , Angle J. S. , Hill R. L. , Welterlen M. S.
Published: July 2010

A study was initiated to examine runoff volume and sediment loss from various density tall fescue (Festuca arundinacea Schreb.) turf stands. Plots were established with seeding rates of 0, 98, 244, 390 and 488 kg ha−1 and allowed to mature for 9 months. Three different rainfall intensities (76, 94, and 120 mm h−1) were applied to the plots using a variable intensity rainfall simulator. Results indicate that there were significant differences in runoff volume and sediment load as affected by rainfall intensity. The runoff initiation time for the 0 kg ha−1 seeding rate was the only seeding rate that was significantly different from all others. Mean runoff rates over time were significantly different for the first 5‐min time interval of the 30‐min storm for all three intensities. There was a significant difference in total sediment load for all three rainfall intensities. At the high (120 mm h−1) rainfall intensity, there was over a sixfold reduction in sediment loss when comparing the 0 kg ha−1 seeding rate to the 98 kg ha−1 seeding rate. Greater sediment loss reductions were observed at the lower rainfall intensifies when comparing the same seeding rates. Sediment loss rates did not differ for the 98, 244, 390, and 488 kg ha−1 seeding rates at the low (76 mm h−1) and medium (94 mm h−1) rainfall intensities. At the high (120 mm h−1) rainfall intensity, significant differences were detected between the 0 kg ha−1 and the 488 kg ha−1 seeding rate. The 98, 244, and 390 kg ha−1 seeding rates were not statistically different at this intensity. These results indicate that even low density turfgruss stands significantly reduce sediment loss.
Sorbed Chemical Transport in Overland Flow: II. Enrichment Ratio Variation with Erosion Processes
Authors: Ghadiri H. , Rose C.W.
Published: July 2010

Breakdown of soil aggregates by rainfall, loss of sediment, and the enrichment of fine particles, organic matter, and N in eroded sediment were measured in flume experiments with a constant rainfall rate of 100 mm h−1. Experiments covering two soil types with different soil surface configurations and slopes were designed to ensure beth exclusion of runoff entrainment as a major erosion factor, and that throughout exposure to rainfall the soil surface was unprotected by any significant depth of water. Sediment concentration differed initially for different experimental configurations, but all approached a single value after equilibrium was attained. Slope length did not have any effect on sediment concentration when rainfall was the only erosive agent at work and no surface rilling occurred. A rainfall‐induced mechanism of transient microrilling has been proposed for sediment transport when there is no significant depth of water or rills under rainfall. Aggregate size distribution of the eroded sediment was drastically different to that of the original soil. The percentage of fine particles in the eroded sediment was more than 50% of the total, while this size fraction constituted less than 5% of the original soil. The proportion of large aggregates in the eroded sediment was less than in the original soil, and the intermediate size fractions remained unchanged. This dramatic production of fine particles is due to direct raindrop impact on the exposed surfaces of soil aggregates. The resulting loss of fine sediment from large aggregates has been termed raindrop stripping, a process that can lead to significant enrichment of any sorbed chemical concentrated in the outer layers of soil aggregates. The peeling action of raindrops was shown to be responsible for the formation of the bulk of fine particles found in eroded sediment. This mechanism, together with the differential concentration of sorbed chemicals within the aggregates, were found to be the main cause of the enrichment of sorbed chemicals in the eroded sediment. The enrichment ratio of organic C and N beth decreased with cumulative soil loss and duration of the erosion event.
Radiocesium Levels in Swedish Moose in Relation to Deposition, Diet, and Age
Authors: Palo R. T. , Nelin P. , Nylen T. , Wickman G.
Published: July 2010

During the hunting season in September 1986 in Västerbotten, Sweden, the mean concentration of 137 Cs in muscle tissue of moose [Alces alces (L.)] was 500 Bq kg−1 (SD = 400) (median = 398) fresh weight in calves, and 300 Bq kg−1 (SD = 250) (median = 253) in adults. In September 1987, the median concentration in calves was 401 Bq kg−1 and 201 Bq kg−1 in adults. In September 1988 the mean concentration of 137 Cs was 1300 Bq kg−1 (SD = 1000) (median = 930) in calves, and 640 Bq kg−1 (SD = 520) (median = 499) in adults. Calves contained about 40% higher activity concentration than adults. A positive correlation between muscle activity and deposition per square meter was evident. Concentration in typical food plants for moose such as bilberry (Vaccinium myrtillus L.) peaked at 2000 Bq kg−1 (SD = 1000) in July 1986 but had declined to about 600 Bq kg−1 (SD = 200) by July 1988. However, in birch (Betula pubescens Ehrh.) the activity concentration did not differ between 1986, 1987 and 1988. Rumen content analyses showed that in 1988, utilization of lingonberry (Vaccinium vitis‐idaea) increased while the proportion of willow (Salix spp.) decreased. No relationship between the proportion of specific plant species in the rumen and flesh activity concentration was noted. An increase in foraging on highly contaminated plant species such as bilberry, aquatic plants and mushrooms in July and August 1988 might explain the rise in concentration in moose in September. Diet selection by animals is an important factor in predicting the uptake of environmental contaminants and the changes in tissue levels of such contaminants with time.