bluuebunny/crossref_metadata_2025 huggingface dataset:
Sequence‐Based Source Tracking of Escherichia coli Based on Genetic Diversity of β‐Glucuronidase
Authors: Ram Jeffrey L. , Ritchie Raquel P. , Fang Jianwen , Gonzales Felicitas S. , Selegean James P.
Published: June 2010

High levels of fecal bacteria are a concern for recreational waters; however, the source of contamination is often unknown. This study investigated whether direct sequencing of a bacterial gene could be utilized for detecting genetic differences between bacterial strains for microbial source tracking. A 525‐nucleotide segment of the gene for β‐glucuronidase (uidA) was sequenced in 941 Escherichia coli isolates from the Clinton River–Lake St. Clair watershed, 182 E. coli isolates from human and animal feces, and 34 E. coli isolates from a combined sewer. Environmental isolates exhibited 114 alleles in 11 groups on a genetic tree. Frequency of strains from different genetic groups differed significantly (p < 0.03) between upstream reaches (Bear Creek–Red Run), downstream reaches, and Lake St. Clair beaches. Fecal E. coli uidA sequences exhibited 81 alleles that overlapped with the environmental set. An algorithm to assign alleles to different host sources averaged approximately 75% correct classification with the fecal data set. Using the same algorithm, the percent of environmental isolates assignable to humans decreased significantly between Bear Creek–Red Run (30 ± 3%) and the beaches (17 ± 2%) (p < 0.05). Birds accounted for approximately 50% of assignable environmental isolates. For combined sewer isolates, the same algorithm assigned 51% to humans. These experiments demonstrate differences in the frequency of different E. coli strains at different locations in a watershed, and provide a “proof in principle” that sequence‐based data can be used for microbial source tracking.
Feasibility and Costs of Phosphorus Application Limits on 39 U.S. Swine Operations
Authors: Lory John A. , Massey Raymond E. , Zulovich Joseph M. , Hoehne John A. , Schmidt Amy M. , Carlson Marcia S. , Fulhage Charles D.
Published: June 2010

Concerns about manure P and water quality have prompted new regulations imposing P limits on land application of manure. Previous research established that P limits increase land needs for animal feeding operations. We evaluated the effect of N, annual P, and rotation P limits on the feasibility of manure management. A mechanistic model characterized manure management practices on 39 swine operations (20 unagitated lagoon and 19 slurry operations) in five states (Iowa, Missouri, North Carolina, Oklahoma, and Pennsylvania). Extensive information collected from each operation was used to determine effects of manure storage type, ownership structure, and application limits on attributes of manure management. Phosphorus limits had substantially greater effect on slurry operations, increasing land needs 250% (0.3 hectares per animal unit [AU]) and time for manure application 24% (2.5 min AU−1) for rotation P limits and 41% (4.4 min AU−1) for annual P limits. Annual P limits were infeasible for current land application equipment on two operations and had the greatest effect on time and costs because they required all but three slurry operations to reduce discharge rate. We recommend implementing rotation P limits (not to exceed crop N need) to minimize time effects, allow most farmers to use their current manure application methods, and allow manure to fulfill crop N and P needs in the year of application. Phosphorus limits increased potential manure value but would require slurry operations to recover at least 61% of manure value through manure sales. Phosphorus limits are likely to shape the U.S. swine industry through differential effects on the various sectors of the swine industry.
Nitrate Removal in Riparian Wetlands
Authors: Rutherford J. C. , Nguyen M. L.
Published: June 2010

Riparian wetlands containing springs are thought to be ineffective at removing nitrate because contact times between the upwelled ground water and the underlying microbially active soils are short. Tracer experiments using lithium bromide (LiBr) and nitrate (NO3–N) injected at the surface were used to quantify residence times and NO3–N removal in a riparian swale characteristic of New Zealand hill‐country pasture. An experimental enclosure was used with collecting trays at the downstream end to measure flow and concentration, shallow wells to measure subsurface concentrations, and an array of logging conductivity probes to monitor tracer continuously. The majority of added tracer reached the outlet more slowly than could be explained by surface flow, but more quickly than could be explained by Darcy seepage flow. There was evidence from the wells of tracer diffusing vertically to a depth of at least 5 cm into the surface soil layer, which was permanently saturated and highly porous. During dry weather 24 ± 9% of added NO3–N was removed over a distance of 1.5 m largely by denitrification. The net uptake length coefficient for this wetland (K = 0.08 ± 0.03 m−1) is slightly higher than the range (K = 0.01–0.07 m−1) measured in a small stream channel infested with macrophytes. Nitrate removal is expected to decrease with increasing flow. Seepage flow is estimated to have removed only 7 ± 4% of the added NO3–N and we hypothesize that vertical diffusion substantially increases NO3–N removal in this type of wetland. Riparian wetlands with springs and surface flows should not be dismissed as having low NO3–N removal potential without checking whether there is significant vertical mixing.
In Situ Dynamics of Phosphorus in the Rhizosphere Solution of Five Species
Authors: Wang Z. Y. , Kelly J. M. , Kovar J. L.
Published: June 2010

Root activity can modify the chemistry of the rhizosphere and alter phosphorus (P) availability and uptake. However, until recently, relatively little was known about the dynamics of soil solution P at the root surface because of our inability to measure in situ changes in solution P at the plant root. A mini‐rhizotron experiment with corn (Zea mays L. cv. Stine 2250), soybean [Glycine max (L.) Merr. cv. Pioneer 3563), cottonwood (Populus deltoids L.), smooth brome (Bromus inermis Leyss.), and switchgrass (Panicum virgatum L.) was conducted to measure the spatial and temporal dynamics of P in the rhizosphere solution of a fine silty, P‐rich calcareous soil (solid‐phase total P concentration = 62 mg kg−1, pH = 7.68) from western Iowa. Micro‐suction cups were used to collect samples of soil solution from defined segments of the rhizosphere, and capillary electrophoresis (CE) was used to determine the P concentration of the soil solution. At the end of 10 d, a decreasing P concentration gradient in soil solution toward the root was observed in corn, cottonwood, and smooth brome. No clear rhizosphere effect was observed for soybean and switchgrass. Statistical analysis indicated significantly lower solution P concentrations in the rhizospheres of corn (p = 0.05), cottonwood (p = 0.01), and smooth brome (p = 0.01) compared with bulk soil solution. Results indicate that P depletion from rhizosphere soil solution depends on plant species. Under the conditions of this study, corn, cottonwood, and smooth brome were more effective in depleting solution P than soybean and switchgrass.
Evaluation of Phosphorus Transport in Surface Runoff from Packed Soil Boxes
Authors: Kleinman Peter J. A. , Sharpley Andrew N. , Veith Tamie L. , Maguire Rory O. , Vadas Peter A.
Published: June 2010

Evaluation of phosphorus (P) management strategies to protect water quality has largely relied on research using simulated rainfall to generate runoff from either field plots or shallow boxes packed with soil. Runoff from unmanured, grassed field plots (1 m wide × 2 m long, 3–8% slope) and bare soil boxes (0.2 m wide and 1 m long, 3% slope) was compared using rainfall simulation (75 mm h−1) standardized by 30‐min runoff duration (rainfall averaged 55 mm for field plots and 41 mm for packed boxes). Packed boxes had lower infiltration (1.2 cm) and greater runoff (2.9 cm) and erosion (542 kg ha−1) than field plots (3.7 cm infiltration; 1.8 cm runoff; 149 kg ha−1 erosion), yielding greater total phosphorus (TP) losses in runoff. Despite these differences, regressions of dissolved reactive phosphorus (DRP) in runoff and Mehlich‐3 soil P were consistent between field plots and packed boxes reflecting similar buffering by soils and sediments. A second experiment compared manured boxes of 5‐ and 25‐cm depths to determine if variable hydrology based on box depth influenced P transport. Runoff properties did not differ significantly between box depths before or after broadcasting dairy, poultry, or swine manure (100 kg TP ha−1). Water‐extractable phosphorus (WEP) from manures dominated runoff P, and translocation of manure P into soil was consistent between box types. This study reveals the practical, but limited, comparability of field plot and soil box data, highlighting soil and sediment buffering in unamended soils and manure WEP in amended soils as dominant controls of DRP transport.
Runoff Phosphorus Losses as Related to Phosphorus Source, Application Method, and Application Rate on a Piedmont Soil
Authors: Tarkalson David D. , Mikkelsen Robert L.
Published: June 2010

Land application of animal manures and fertilizers has resulted in an increased potential for excessive P losses in runoff to nutrient‐sensitive surface waters. The purpose of this research was to measure P losses in runoff from a bare Piedmont soil in the southeastern United States receiving broiler litter or inorganic P fertilizer either incorporated or surface‐applied at varying P application rates (inorganic P, 0–110 kg P ha−1; broiler litter, 0–82 kg P ha−1). Rainfall simulation was applied at a rate of 76 mm h−1 Runoff samples were collected at 5‐min intervals for 30 min and analyzed for reactive phosphorus (RP), algal‐available phosphorus (AAP), and total phosphorus (TP). Incorporation of both P sources resulted in P losses not significantly different than the unfertilized control at all application rates. Incorporation of broiler litter decreased flow‐weighted concentration of RP in runoff by 97% and mass loss of TP in runoff by 88% compared with surface application. Surface application of broiler litter resulted in runoff containing between 2.3 and 21.8 mg RP L−1 for application rates of 8 to 82 kg P ha−1, respectively. Mass loss of TP in runoff from surface‐applied broiler litter ranged from 1.3 to 8.5 kg P ha−1 over the same application rates. Flow‐weighted concentrations of RP and mass losses of TP in runoff were not related to application rate when inorganic P fertilizer was applied to the soil surface. Results for this study can be used by P loss assessment tools to fine‐tune P source, application rate, and application method site factors, and to estimate extreme‐case P loss from cropland receiving broiler litter and inorganic P fertilizers.
Sources and Transformations of Nitrogen Compounds along the Lower Jordan River
Authors: Segal‐Rozenhaimer Michal , Shavit Uri , Vengosh Avner , Gavrieli Ittai , Farber Efrat , Holtzman Ran , Mayer Bernhard , Shaviv Avi
Published: June 2010

The Lower Jordan River is located in the semiarid area of the Jordan Valley, along the border between Israel and Jordan. The implementation of the water sections of the peace treaty between Israel and Jordan and the countries' commitment to improve the ecological sustainability of the river system require a better understanding of the riverine environment. This paper investigates the sources and transformations of nitrogen compounds in the Lower Jordan River by applying a combination of physical, chemical, isotopic, and mathematical techniques. The source waters of the Lower Jordan River contain sewage, which contributes high ammonium loads to the river. Ammonium concentrations decrease from 20 to 0–5 mg N L−1along the first 20 km of the Lower Jordan River, while nitrate concentrations increase from nearly zero to 10–15 mg N L−1, and δ15N (NO3) values increase from less than 5‰ to 15–20‰. Our data analysis indicates that intensive nitrification occurs along the river, between 5 and 12 km from the Sea of Galilee, while further downstream nitrate concentration increases mostly due to an external subsurface water source that enters the river.
Nutrient Input and Removal Trends for Agricultural Soils in Nine Geographic Regions in Arkansas
Authors: Slaton Nathan A. , Brye Kristofor R. , Daniels Mike B. , Daniel Tommy C. , Norman Richard J. , Miller David M.
Published: June 2010

Knowledge of the balance between nutrient inputs and removals is required for identifying regions that possess an excess or deficit of nutrients. This assessment describes the balance between the agricultural nutrient inputs and removals for nine geographical districts within Arkansas from 1997 to 2001. The total N, P, and K inputs were summed for each district and included inorganic fertilizer and collectable nutrients excreted as poultry, turkey, dairy, and hog manures. Nutrients removed by harvested crops were summed and subtracted from total nutrient inputs to calculate the net nutrient balance. The net balances for N, P, and K were distributed across the hectarage used for row crop, hay, pasture, or combinations of these land uses. Row‐crop agriculture predominates in the eastern one‐third and animal agriculture predominates in the western two‐thirds of Arkansas. Nutrients derived from poultry litter accounted for >92% of the total transportable manure N, P, and K. The three districts in the eastern one‐third of Arkansas contained 95% of the row‐crop hectarage and had net N and P balances that were near zero or negative. The six districts in the western two‐thirds of Arkansas accounted for 89 to 100% of the animal populations, had positive net balances for N and P, and excess P ranged from 1 to 9 kg P ha−1 when distributed across row‐crop, hay, and pasture hectarage. Transport of excess nutrients, primarily in poultry litter, outside of the districts in western Arkansas is needed to achieve a balance between soil inputs and removals of P and N.
Phosphorus in Surface Runoff from Calcareous Arable Soils of the Semiarid Western United States
Authors: Turner Benjamin L. , Kay Mary A. , Westermann Dale T.
Published: June 2010

Management strategies that minimize P transfer from agricultural land to water bodies are based on relationships between P concentrations in soil and runoff. This study evaluated such relationships for surface runoff generated by simulated sprinkler irrigation onto calcareous arable soils of the semiarid western United States. Irrigation was applied at 70 mm h−1to plots on four soils containing a wide range of extractable P concentrations. Two irrigation events were conducted on each plot, first onto dry soil and then after 24 h onto wet soil. Particulate P (>0.45 μm) was the dominant fraction in surface runoff from all soils and was strongly correlated with suspended sediment concentration. For individual soil types, filterable reactive P (<0.45 μm) concentrations were strongly correlated with all soil‐test P methods, including environmental tests involving extraction with water (1:10 and 1:200 soil to solution ratio), 0.01MCaCl2, and iron strips. However, only the Olsen‐P agronomic soil‐test procedure gave models that were not significantly different among soils. Soil chemical differences, including lower CaCO3and water‐extractable Ca, higher water‐extractable Fe, and higher pH, appeared to account for differences in filterable reactive P concentrations in runoff from soils with similar extractable P concentrations. It may therefore be possible to use a single agronomic test to predict filterable reactive P concentrations in surface runoff from calcareous soils, but inherent dangers exist in assuming a consistent response, even for one soil within a single field.
Effect of Poultry Diet on Phosphorus in Runoff from Soils Amended with Poultry Manure and Compost
Authors: Vadas P. A. , Meisinger J. J. , Sikora L. J. , McMurtry J. P. , Sefton A. E.
Published: June 2010

Phosphorus in runoff from fields where poultry litter is surface‐applied is an environmental concern. We investigated the effect of adding phytase and reducing supplemental P in poultry diets and composting poultry manures, with and without Fe and Al amendments, on P in manures, composts, and runoff. We used four diets: normal (no phytase) with 0.4% supplemental P, normal + phytase, phytase + 0.3% P, and phytase + 0.2% P. Adding phytase and decreasing supplemental P in diets reduced total P but increased water‐extractable P in manure. Compared with manures, composting reduced both total P, due to dilution of manure with woodchips and straw, and water‐extractable P, but beyond a dilution effect so that the ratio of water‐extractable P to total P was less in compost than manure. Adding Fe and Al during composting did not consistently change total P or water‐extractable P. Manures and composts were surface‐applied to soil boxes at a rate of 50 kg total P ha−1 and subjected to simulated rainfall, with runoff collected for 30 min. For manures, phytase and decreased P in diets had no significant effect on total P or molybdate‐reactive P loads (kg ha−1) in runoff. Composting reduced total P and molybdate‐reactive P loads in runoff, and adding Fe and Al to compost reduced total P but not molybdate‐reactive P loads in runoff. Molybdate‐reactive P in runoff (mg box−1) was well correlated to water‐extractable P applied to boxes (mg box−1) in manures and composts. Therefore, the final environmental impact of dietary phytase will depend on the management of poultry diets, manure, and farm‐scale P balances.
Nitrogen, Phosphorus, and Potassium Uptake by Wheat and Their Distribution in Soil following Successive, Annual Compost Applications
Authors: Bar‐Tal A. , Yermiyahu U. , Beraud J. , Keinan M. , Rosenberg R. , Zohar D. , Rosen V. , Fine P.
Published: June 2010

The overall objective of the present study was to determine the loading limits of composts that should be applied annually to irrigated wheat. We conducted a container experiment in a greenhouse during four years. It included eight treatments: sewage sludge compost (SSC) and cattle manure compost (CMC), each applied annually to a sandy soil, at rates equivalent to 3, 6, and 12 kg m−2, and two controls, one fertilized and one unfertilized. Total dry matter (DM), grain production, and the amount of N, P, and K taken up by plants increased with increasing compost rate. Nitrogen uptake by the plants of the fertilized control was much higher than by the plants of the highest compost rate. Phosphorus and K uptake by the plants amended with the highest compost rate was much higher than by the fertilized control plants. Inorganic N quantity in the soil increased with increasing compost rate and with successive applications. The net N mineralization during the first year of wheat growth was very low, less than 3.5% of the applied organic N under all compost application rates. The contribution of the organic N mineralization increased during the second and third years. Most of the N increase in the compost treatment was found in the upper layer of 0 to 15 cm, whereas in the fertilized treatment N accumulated from the surface to the bottom of the container, 0 to 55 cm. The successive application of high rates of composts resulted in P and K accumulation in the soil profile.
Estimating Bulk Density in Vertically Exposed Stoney Alluvium Using a Modified Excavation Method
Authors: Brye K. R. , Morris T. L. , Miller D. M. , Formica S. J. , Van Eps M. A.
Published: June 2010

Despite many decades of education and refining land‐use practices, accelerated stream bank erosion is still prevalent in the United States. Eroding stream banks produce a sediment load to the riverine system and can cause reduced water quality as a result of increased suspended sediment. As total maximum daily loads (TMDLs) for water bodies impaired by turbidity or suspended sediments become more numerous, a simple, in situ field technique will be needed to estimate the bulk density of readily erodible stream bank material so that reasonably accurate sediment loading rates can be estimated. In this study, the excavation/polyurethane‐foam technique for estimating total bulk density was applied to vertically exposed alluvium with high coarse‐fragment content. Though not previously attempted in vertically exposed alluvium with high coarse‐fragment content, the excavation/polyurethane‐foam technique appears to provide a reasonably accurate estimate of the total and soil (<2‐mm size fraction) bulk density from vertically exposed, alluvial deposits with high coarse‐fragment content (i.e., >70%) along eroding stream banks. Obtaining bulk density estimates using this method would facilitate calculation of sediment loading rates to riverine systems with actual field data.
Adsorption of Trace Metals on Glass Fiber Filters
Authors: Fuhrmann Mark , Fitts Jeffrey P.
Published: June 2010

Filters, containing glass‐fiber (GF) filter material, are commonly used as the primary filter or as the prefilter in sampling natural waters and laboratory experiments with high concentrations of suspended solids. We observed that GF filter material removed substantial quantities of trace metals from solutions of low ionic strength at near neutral and slightly acidic pH. The GF material sorbed essentially all Pb and Ag from 5‐mL aliquots of solutions containing 0.054 and 0.093 mM, respectively. Somewhat less Ni was sorbed from a 0.099 mM solution. This material retained about 43 μmol of Ag per gram of GF material (4600 μg/g). The Ag and Ni sorption was highest at low KNO3 concentrations (as background electrolyte) and decreased to a constant concentration of sorbed metal at approximately 10 mM KNO3 Glass‐fiber filter material should only be used with careful testing for the elements of concern under conditions that closely match expected environmental or experimental conditions.
An Economic Evaluation of Livestock Odor Regulation Distances
Authors: Bazen Ernest F. , Fleming Ronald A.
Published: June 2010

Setback regulations—legislated distances that livestock production facilities must be removed from surrounding properties—are meant to mitigate odor impacts. If the setback length is too short, then there is evidence that surrounding properties and people suffer uncompensated damages. If, on the other hand, setback lengths are too long, then livestock producers may be paying more than that required to compensate for odor‐related environmental damages. The purpose of this study is to assess the impact of Kentucky's livestock production facility setbacks on the value of surrounding properties and farm financial management decisions. This paper develops a model of the benefits of livestock odor reduction and the livestock odor abatement cost associated with setback lengths paid by producers. The results of this investigation indicate that the mandated setback lengths for Kentucky are too short. Livestock production firms are worse off under longer setback lengths, but the losses to surrounding home owners far exceed the firm gains at the mandated setbacks. A finding of this study is that the firm has no incentive to completely protect the legislated setback length. Livestock producers in compliance with the relevant setback length may feel protected from odor lawsuits despite damage being done to surrounding property. This suggests that the perceived threat of lawsuit is currently low in the state of Kentucky. Both industry and public goals could be met from further research including location and economic impact of livestock production.
Monitoring Nitrogen Deposition in Throughfall Using Ion Exchange Resin Columns: A Field Test in the San Bernardino Mountains
Authors: Fenn Mark E. , Poth Mark A.
Published: June 2010

Conventional throughfall collection methods are labor intensive and analytically expensive to implement at broad scales. This study was conducted to test an alternative approach requiring infrequent sample collection and a greatly reduced number of chemical analyses. The major objective of the study was to determine the feasibility of using ion exchange resin (IER) to measure N deposition in throughfall with field deployment periods of 3 to 12 mo. Nitrogen deposition measurements in bulk throughfall collected under pine (Pinus sp.) canopies and in forest clearings were compared between co‐located conventional throughfall solution collectors and IER throughfall collectors using mixed bed IER columns. Deposition data were collected for 1 yr at a high deposition site (Camp Paivika, CP) and a relatively low one (Barton Flats, BF) in the San Bernardino Mountains in southern California: Annual throughfall deposition values (kg ha−1 of NH4–N + NO3–N) under large ponderosa pine trees (Pinus ponderosa Laws.) were 145.8 and 143.9 at CP and 17.0 and 15.0 at BF according to the IER and conventional methods, respectively. Analogous values for bulk deposition in forest clearings were 15.6 and 12.3 at CP and 4.0 and 3.3 at BF. It was concluded that the IER collectors can be used for routine monitoring of deposition in throughfall and bulk deposition, provided that field blanks are used to account for background levels of N in the IER columns, which at times are slightly elevated, possibly from slow release of amine groups from the anion exchange resin during field exposures.
Biological Reduction of Chlorate in a Gas‐Lift Reactor Using Hydrogen as an Energy Source
Authors: Kroon A. G. M. , van Ginkel C. G.
Published: June 2010

Chlorate release into the environment occurs with its manufacture and use. Biological reduction of chlorate offers an attractive option to decrease this release. A hydrogen gas‐lift reactor with microorganisms attached to pumice particles was used for the treatment of wastewater containing high concentrations of chlorate. The microorganisms used chlorate as an electron acceptor and hydrogen gas as a reducing agent. After a start‐up period of only a few weeks, chlorate reduction rates of 3.2 mmol L−1 h−1 were achieved during continuous operation. During this period, a hydrogen consumption rate of 14.5 mmol L−1 h−1 was observed. Complete removal of chlorate was maintained at hydraulic retention times of 6 h. This study clearly demonstrates the potential of hydrogen gas‐lift bioreactors for the treatment of chlorate‐containing waste streams.
Mechanisms of Thorium Migration in a Semiarid Soil
Authors: Bednar A. J. , Gent D. B. , Gilmore J. R. , Sturgis T. C. , Larson S. L.
Published: June 2010

Thorium concentrations at Kirtland Air Force Base training sites in Albuquerque, NM, have been previously described; however, the mechanisms of thorium migration were not fully understood. This work describes the processes affecting thorium mobility in this semiarid soil, which has implications for future remedial action. Aqueous extraction and filtration experiments have demonstrated the colloidal nature of thorium in the soil, due in part to the low solubility of thorium oxide. Colloidal material was defined as that removed by a 0.22‐μm or smaller filter after being filtered to nominally dissolved size (0.45 μm). Additionally, association of thorium with natural organic matter is suggested by micro‐ and ultrafiltration methods, and electrokinetic data, which indicate thorium migration as a negatively charged particle or anionic complex with organic matter. Soil fractionation and digestion experiments show a bimodal distribution of thorium in the largest and smallest size fractions, most likely associated with detrital plant material and inorganic oxide particles, respectively. Plant uptake studies suggest this could also be a mode of thorium migration as plants grown in thorium‐containing soil had a higher thorium concentration than those in control soils. Soil erosion laboratory experiments with wind and surface water overflow were performed to determine bulk soil material movement as a possible mechanism of mobility. Information from these experiments is being used to determine viable soil stabilization techniques at the site to maintain a usable training facility with minimal environmental impact.
Fluometuron and Pendimethalin Runoff from Strip and Conventionally Tilled Cotton in the Southern Atlantic Coastal Plain
Authors: Potter Thomas L. , Truman Clint C. , Bosch David D. , Bednarz Craig
Published: June 2010

In the Atlantic Coastal Plain region of southern Georgia (USA), cotton (Gossypium hirsutum L.) acreage increased threefold in the past decade. To more effectively protect water quality in the region, best management practices are needed that reduce pesticide runoff from fields in cotton production. This study compared runoff of two herbicides, fluometuron [N,N‐dimethyl‐N′‐[3‐(trifluoromethyl)‐phenyl]‐urea] and pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitro‐benzenamine], from plots in strip‐tillage (ST) and conventional‐tillage (CT) management near Tifton, GA. Rainfall simulations were conducted one day after preemergence herbicide applications to 0.0006‐ha plots and runoff from 0.15‐ha plots due to natural rainfall following preemergence pendimethalin and fluometuron and postemergence fluometuron use was monitored. Pendimethalin runoff was greater under CT than ST due to strong pendimethalin soil sorption and higher erosion and runoff under CT. The highest losses, 1.3% of applied in CT and 0.22% of applied in ST, were observed during rainfall simulations conducted 1 DAT. Fluometuron runoff from natural rainfall was substantially lower from ST than from CT plots but the trend was reversed in rainfall simulations. In all studies, fluometuron runoff was also relatively low (<1% of applied), and on plots under natural rainfall, desmethylfluometuron (DMF) represented about 50% of total fluometuron runoff. Fluometuron's relatively low runoff rate appeared linked to its rapid leaching, and high DMF detection rates in runoff support DMF inclusion in fluometuron risk assessments. Results showed that ST has the potential to reduce runoff of both herbicides, but fluometuron leaching may be a ground water quality concern.
Evaluation of the Phosphorus Source Component in the Phosphorus Index for Pastures
Authors: DeLaune P. B. , Moore P. A. , Carman D. K. , Sharpley A. N. , Haggard B. E. , Daniel T. C.
Published: June 2010

A phosphorus (P) index for pastures was developed to write nutrient management plans that determine how much P can be applied to a given field. The objectives of this study were to (i) evaluate and compare the P index for pastures, particularly the P source component, and an environmental threshold soil test P level by conducting rainfall simulations on contrasting soils under various management scenarios; and (ii) evaluate the P index for pastures on field‐scale watersheds. Poultry litter was applied to 12 small plots on each of six farms based on either an environmental threshold soil test P level or on the P index for pastures, and P runoff was evaluated using rainfall simulators. The P index was also evaluated from two small (0.405 ha) watersheds that had been fertilized annually with poultry litter since 1995. Results from the small plot study showed that soil test P alone was a poor predictor of P concentrations in runoff water following poultry litter applications. The relationship between P in runoff and the amount of soluble P applied was highly significant. Furthermore, P concentrations in runoff from plots with and without litter applications were significantly correlated to P index values. Studies on pastures receiving natural rainfall and annual poultry litter applications indicated that the P index for pastures predicted P loss accurately without calibration (y = 1.16x − 0.23, r2 = 0.83). These data indicate that the P index for pastures can accurately assess the risk of P loss from fields receiving poultry litter applications in Arkansas and provide a more realistic risk assessment than threshold soil test P levels.
Decreasing Phosphorus Runoff Losses from Land‐Applied Poultry Litter with Dietary Modifications and Alum Addition
Authors: Smith Douglas R. , Moore P. A. , Miles D. M. , Haggard B. E. , Daniel T. C.
Published: June 2010

Phosphorus (P) losses from pastures fertilized with poultry litter contribute to the degradation of surface water quality in the United States. Dietary modification and manure amendments may reduce potential P runoff losses from pastures. In the current study, broilers were fed a normal diet, phytase diet, high available phosphorus (HAP) corn diet, or HAP corn + phytase diet. Litter treatments were untreated control and alum added at 10% by weight between flocks. Phytase and HAP corn diets reduced litter dissolved P content in poultry litter by 10 and 35%, respectively, compared with the normal diet (789 mg P kg−1). Alum treatment of poultry litter reduced the amount of dissolved P by 47%, while a 74% reduction was noted after alum treatment of litter from the HAP corn + phytase diet. The P concentrations in runoff water were highest from plots receiving poultry litter from the normal diet, whereas plots receiving poultry litter from phytase and HAP corn diets had reduced P concentrations. The addition of alum to the various poultry litters reduced P runoff by 52 to 69%; the greatest reduction occurred when alum was used in conjunction with HAP corn and phytase. This study demonstrates the potential added benefits of using dietary modification in conjunction with manure amendments in poultry operations. Integrators and producers should consider the use of phytase, HAP corn, and alum to reduce potential P losses associated with poultry litter application to pastures.
Water Quality Impacts of Converting to a Poultry Litter Fertilization Strategy
Authors: Harmel R. D. , Torbert H. A. , Haggard B. E. , Haney R. , Dozier M.
Published: June 2010

When improperly managed, land application of animal manures can harm the environment; however, limited watershed‐scale runoff water quality data are available to research and address this issue. The water quality impacts of conversion to poultry litter fertilization on cultivated and pasture watersheds in the Texas Blackland Prairie were evaluated in this three‐year study. Edge‐of‐field N and P concentrations and loads in surface runoff from new litter application sites were compared with losses under inorganic fertilization. The impact on downstream nutrient loss was also examined. In the fallow year with no fertilizer application, nutrient losses averaged 3 kg N ha−1 and 0.9 kg P ha−1 for the cultivated watersheds and were below 0.1 kg ha−1 for the pasture watersheds. Following litter application, PO4–P concentrations in runoff were positively correlated to litter application rate and Mehlich‐3 soil P levels. Following litter application, NO3–N and NH4–N concentrations in runoff were typically greater from cultivated watersheds, but PO4–P concentrations were greater for the pasture watersheds. Total N and P loads from the pasture watersheds (0.2 kg N ha−1 and 0.7 kg P ha−1) were significantly lower than from the cultivated watersheds (32 kg N ha−1 and 5 kg P ha−1) partly due to lower runoff volumes from the pasture watersheds. Downstream N and P concentrations and per‐area loads were much lower than from edge‐of‐field watersheds. Results demonstrate that a properly managed annual litter application (4.5 Mg ha−1 or less depending on litter N and P content) with supplemental N should supply necessary nutrients without detrimental water quality impacts.
Interrelationship of Macropores and Subsurface Drainage for Conservative Tracer and Pesticide Transport
Authors: Fox Garey A. , Malone Rob , Sabbagh George J. , Rojas Ken
Published: June 2010

Macropore flow results in the rapid movement of pesticides to subsurface drains, which may be caused in part by a small portion of macropores directly connected to drains. However, current models fail to account for this direct connection. This research investigated the interrelationship between macropore flow and subsurface drainage on conservative solute and pesticide transport using the Root Zone Water Quality Model (RZWQM). Potassium bromide tracer and isoxaflutole, the active ingredient in BALANCE herbicide [(5‐cyclopropyl‐4‐isoxazolyl) [2(methylsulfonyl)‐4‐(trifluoromethyl)phenyl] methanone], with average half‐life of 1.7 d were applied to a 30.4‐ha Indiana corn (Zea mays L.) field. Water flow and chemical concentrations emanating from the drains were measured from two samplers. Model predictions of drain flow after minimal calibration reasonably matched observations (slope = 1.03, intercept = 0.01, and R2 = 0.75). Without direct hydraulic connection of macropores to drains, RZWQM under predicted bromide and isoxaflutole concentration during the first measured peak after application (e.g., observed isoxaflutole concentration was between 1.2 and 1.4 μg L−1, RZWQM concentration was 0.1 μg L−1). This research modified RZWQM to include an express fraction relating the percentage of macropores in direct hydraulic connection to drains. The modified model captured the first measured peak in bromide and isoxaflutole concentrations using an express fraction of 2% (e.g., simulated isoxaflutole concentration increased to 1.7 μg L−1). The RZWQM modified to include a macropore express fraction more accurately simulates chemical movement through macropores to subsurface drains. An express fraction is required to match peak concentrations in subsurface drains shortly after chemical applications.
Field Water Balance of Landfill Final Covers
Authors: Albright William H. , Benson Craig H. , Gee Glendon W. , Roesler Arthur C. , Abichou Tarek , Apiwantragoon Preecha , Lyles Bradley F. , Rock Steven A.
Published: June 2010

Landfill covers are critical to waste containment, yet field performance of specific cover designs has not been well documented and seldom been compared in side‐by‐side testing. A study was conducted to assess the ability of landfill final covers to control percolation into underlying waste. Conventional covers employing resistive barriers as well as alternative covers relying on water‐storage principles were monitored in large (10 × 20 m), instrumented drainage lysimeters over a range of climates at 11 field sites in the United States. Surface runoff was a small fraction of the water balance (0–10%, 4% on average) and was nearly insensitive to the cover slope, cover design, or climate. Lateral drainage from internal drainage layers was also a small fraction of the water balance (0–5.0%, 2.0% on average). Average percolation rates for the conventional covers with composite barriers (geomembrane over fine soil) typically were less than 12 mm/yr (1.4% of precipitation) at humid locations and 1.5 mm/yr (0.4% of precipitation) at arid, semiarid, and subhumid locations. Average percolation rates for conventional covers with soil barriers in humid climates were between 52 and 195 mm/yr (6–17% of precipitation), probably due to preferential flow through defects in the soil barrier. Average percolation rates for alternative covers ranged between 33 and 160 mm/yr (6 and 18% of precipitation) in humid climates and generally less than 2.2 mm/yr (0.4% of precipitation) in arid, semiarid, and subhumid climates. One‐half (five) of the alternative covers in arid, semiarid, and subhumid climates transmitted less than 0.1 mm of percolation, but two transmitted much more percolation (26.8 and 52 mm) than anticipated during design. The data collected support conclusions from other studies that detailed, site‐specific design procedures are very important for successful performance of alternative landfill covers.
Structural and Sorption Characteristics of Adsorbed Humic Acid on Clay Minerals
Authors: Wang Kaijun , Xing Baoshan
Published: June 2010

Clay–humic complexes are commonly distributed in natural environments. They play very important roles in regulating the transport and retention of hydrophobic organic contaminants in soils and sediments. This study examined the structural changes of humic acid (HA) after adsorption by clay minerals and determined phenanthrene sorption by clay–humic complexes. Solid‐ and liquid‐state 13C nuclear magnetic resonance (NMR), for the first time, provided direct evidence for HA fractionation during adsorption on mineral surfaces, that is, aliphatic fractions were preferentially adsorbed by clay minerals while aromatic fractions were left in the solution. The ratio of UV absorbance of HA at 465 and 665 nm (E4 to E6 ratio), which is related to aromaticity, corroborated with the NMR results. For both montmorillonite and kaolinite, adsorbed HA fractions had higher sorption linearity (N) and affinity (Koc) than the source HA. The Koc of adsorbed HA for the clay–humic complexes could be up to several times higher than that of the source HA. This large increase may be contributed by the low polarity of the bound HA. Moreover, for each mineral, the N values of adsorbed HA increased with increasing HA loading. It is believed that HA may develop a more condensed structure on mineral surface at lower HA loading level due to the stronger interactions between HA and mineral surface as a result of close contacts.
Straining, Attachment, and Detachment of Cryptosporidium Oocysts in Saturated Porous Media
Authors: Bradford S. A. , Bettahar M.
Published: June 2010

Accurate knowledge of the transport and deposition behavior for pathogenic Cryptosporidium parvum oocysts is needed to assess contamination and protect water resources. Experimental and modeling studies were undertaken to examine the roles of attachment, detachment, and straining on oocyst transport and retention. Saturated column studies were conducted using Ottawa aquifer sands (U.S. Silica, Ottawa, IL) with median grain sizes of 710, 360, and 150 μm. Decreasing the median sand size tended to produce lower effluent concentrations, greater oocyst retention in the sand near the column inlet, and breakthrough of oocysts at later times. Oocyst transport data also exhibited concentration tailing. Mathematical modeling of the oocyst transport data using fitted first‐order attachment and detachment coefficients provided a satisfactory description of the observed effluent concentration curves, but a poor characterization of the oocyst spatial distribution. Modeling of these data using an irreversible straining term that is depth dependent provided a better description of the oocyst spatial distribution, but could not account for the observed effluent concentration tailing or late breakthrough times. A more physically realistic description of the data was obtained by modeling attachment, detachment, and straining. The percentage of total oocysts retained by straining was estimated from effluent mass balance considerations to be 68% for 710‐μm sand, 79% for 360‐μm sand, and 87% for 150‐μm sand. Straining coefficients were then selected to achieve these percentages of total oocyst retention, and attachment and detachment coefficients were fitted to the effluent concentration curves. Dramatic differences in the predicted oocyst breakthrough curves were observed at greater transport distances for the various model formulations (inclusion or exclusion of straining). Justification for oocyst straining was provided by trends in the transport data, simulation results, pore size distribution information, and published literature.
In Situ Ground Water Denitrification in Stratified, Permeable Soils Underlying Riparian Wetlands
Authors: Kellogg D. Q. , Gold A. J. , Groffman P. M. , Addy K. , Stolt M. H. , Blazejewski G.
Published: June 2010

The ground water denitrification capacity of riparian zones in deep soils, where substantial ground water can flow through low‐gradient stratified sediments, may affect watershed nitrogen export. We hypothesized that the vertical pattern of ground water denitrification in riparian hydric soils varies with geomorphic setting and follows expected subsurface carbon distribution (i.e., abrupt decline with depth in glacial outwash vs. negligible decline with depth in alluvium). We measured in situ ground water denitrification rates at three depths (65, 150, and 300 cm) within hydric soils at four riparian sites (two per setting) using a15N‐enriched nitrate “push–pull” method. No significant difference was found in the pattern and magnitude of denitrification when grouping sites by setting. At three sites there was no significant difference in denitrification among depths. Correlations of site characteristics with denitrification varied with depth. At 65 cm, ground water denitrification correlated with variables associated with the surface ecosystem (temperature, dissolved organic carbon). At deeper depths, rates were significantly higher closer to the stream where the subsoil often contains organically enriched deposits that indicate fluvial geomorphic processes. Mean rates ranged from 30 to 120 μg N kg−1d−1within 10 m versus <1 to 40 μg N kg−1d−1at >30 m from the stream. High denitrification rates observed in hydric soils, down to 3 m within 10 m of the stream in both alluvial and glacial outwash settings, argue for the importance of both settings in evaluating the significance of riparian wetlands in catchment‐scale N dynamics.
Influence of Phytase on Water‐Soluble Phosphorus in Poultry and Swine Manure
Authors: Angel C. Roselina , Powers Wendy J. , Applegate Todd J. , Tamim Nada M. , Christman Mary C.
Published: June 2010

The effect of dietary non‐phytin phosphorus (NPP) and phytase (PHY) concentration on total phosphorus (TP) and water‐soluble phosphorus (WSP) excretion was determined. Diets tested in broiler experiments were: National Research Council nutrient requirements for non‐phytin phosphorus (NRC), NRC + PHY, reduced non‐phytin phosphorus (RED), and RED + PHY. Turkey and swine experiment diets included NRC, RED, and RED + PHY. For all experiments, except broiler Experiment 1, excreta were: (i) boiled, antibiotic added, then frozen; (ii) boiled, antibiotic added, incubated (37°C for 72 h), then frozen; and (iii) incubated, boiled, antibiotic added, then frozen. In Experiment 1, excreta were collected and frozen or incubated for 24 or 48 h. In broiler Experiment 1, WSP was not affected by phytase but increased with post‐excretion incubation. In a broiler Experiment 2, reducing NPP resulted in reduced excreta TP and WSP (11.3 to 8.3 and 5.3 to 2.7 g kg−1). Feeding RED + PHY diets resulted in less TP and WSP (7.6 and 0.6 g kg−1) as compared with NRC + PHY (11.2 and 3.9 g kg−1, Experiment 3). Incubation resulted in increased WSP, irrespective of phytase addition such that WSP as a percent of TP was similar among treatments. Addition of antibiotics before incubation prevented the increase in WSP. Similar results were observed with turkey and swine. Therefore, when phytase is used properly (i.e., with a simultaneous reduction of NPP), WSP or WSP as a percent of TP are not affected. The increase in WSP as a percent of TP post‐excretion is a function of excreta microbial activity and not dietary phytase addition.