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Browsing by Author "Reneau, Raymond B. Jr."

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    Alfalfa growth on acid soil as influenced by Al, Ca, pH and Mo
    Rechcigl, John E. (Virginia Polytechnic Institute and State University, 1986)
    Soil acidity is a major cause of low yields of alfalfa (Medicago sativa L.) in the southeastern United States. Two field experiments were conducted on an Ernest silt loam soil (fine—loamy, mixed, mesic Aquic Fragiudult) to determine what conditions are necessary for optimal alfalfa growth in an acid soil environment. In the first experiment alfalfa was no—till planted to evaluate the influence of surface applied dolomitic limestone at 0 and 6.7 Mg/ha either 8 or 20 months before planting and at planting on alfalfa performance under acidic conditions. Yield increases, greater than two fold, resulted from surface application of limestone regardless of time of application. In the second field experiment treatments included surface and incorporated dolomitic limestone at either 6.5 or 13.0 Mg/ha, gypsum at 13.0 Mg/ha, foliar Mo at 560 g/ha and N as a split. Yields increased in response to surface and incorporated lime, Ca, Mo and N application, possibly as a result of Al activities in soil solution being as low as 0 and 0.05 uM in the surface and 1 m depth samples, respectively, for the surface limed soils. Low activity of Al in soil solution may explain why subsurface acidity was not toxic to alfalfa grown on these soils. This study showed that surface limestone at half the recommended rate is adequate for the growth of alfalfa under acidic conditions. The implanted soil mass technique was used to evaluate the influence of subsurface amendments (Ca, N, Ca and N, KOH and Ca(OH)2) on alfalfa root growth and N fixation on soils that received either 0 or 6.7 Mg/ha surface applied limestone. Of the various subsurface amendments the Ca(OH)2 treatment produced the most root growth and N fixation. This study showed that both the reduction in acidity and the availability of Ca are necessary for optimal N fixation and root growth. In vitro studies conducted in growth pouches showed that pH 4.5 nutrient solution was not ·detrimental to alfalfa growth unless A1 was present. Addition of 3.0 mM Ca to a nutrient solution containing 0.08 mM Al alleviated toxic effects of Al on alfalfa growth. No-till alfalfa can thus be grown on acid soils with surface lime by providing Ca and reducing acidity.
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    Availability and distribution of heavy metals from sewage sludge in the plant-soil continuum
    Rappaport, Bruce D. (Virginia Polytechnic Institute and State University, 1986)
    An investigation was conducted using in situ lysimeters (1.5 m x 2.3 m) to determine Cd, Cu, Ni, and Zn availabilities for barley (Hordeum vulgare L.) and corn (Zea mays L.) grown on four sludge-amended soils. These lysimeters were constructed in Acredale silt loam (Typic Ochraqualf), Bojac loamy sand (Typic Hapludult), Davidson clay loam (Rhodie Paleudult), and Groseclose silt loam (Typic Hapludult) soils. An aerobically digested sewage sludge from a sewage system with major industrial inputs was applied at rates of 0, 42, and 84 dry Mg ha-t to the lysimeters in the poorly-drained Acredale soil. Rates of 0, 42, 84, 126, 168, and 210 dry Mg ha-1 were applied to the lysimeters in the well-drained Bojac, Davidson, and Groseclose soils. Tissue metal concentrations were determined in 1984 and 1985 for a three crop rotation, which consisted of corn, barley, and corn on the Acredale soil. Increases in sludge-borne Ni and Zn led to increases in Ni and Zn concentrations in corn earleaf, corn grain, and barley silage. Copper concentration was increased in barley silage but not in corn grain and stover. On this poorly-drained soil, metal movement did not occur below the Ap horizon even when Cu was applied in excess of USEPA guidelines. Although there were increases in metal levels, all four metals were within the range considered normal for corn and barley growth. Soil, corn, and barley plants were sampled in 1984 and 1985 to determine Cd, Cr, Cu, Ni, and Zn availabilities for crops grown on the sludge-amended Bojac, Davidson, and Groseclose soils. Levels of DTPA-extractable Cd, Cu, Ni, and Zn in the Ap horizon of these soils increased linearly with sludge rate. Corn grain and stover yields were not decreased on the Bojac, Davidson, and Groseclose soils when 4.5, 5105, 760, 43.0, 135, and 620 kg ha-1 of Cd, Cr, Cu, Ni, Pb, and Zn were added as a sludge-amendment. Copper and Zn applied in excess of 480 and 60 kg ha- 1 of USEPA guidelines, respectively on the Bojac, Davidson, and Groseclose soils were not phytotoxic to corn plants in 1984. Corn and barley tissue sampled for three consecutive seasons had Cr concentrations <2.8 mg kg-1.
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    Availability and distribution of nitrogen and phosphorus from sewage sludge in the plant-soil-water continuum
    Scott, James D. (Virginia Tech, 1987-05-05)
    Research was conducted in 1984 and 1985 to determine N and P availabilities for barley (Hordeum vulgare L.) and com ( Zea mays L.) grown on four sludge-amended soils. Tests were conducted on the Acredale silt loam (Typic Ochraquall), Bojac loamy sand (Typic Hapludult), Davidson clay loam (Rhodic Paleudult), and Groseclose silt loam (Typic Hapludult) soils. An aerobically·digested sewage sludge from a sewage treatment plant with major industrial irrputs was applied at rates of 0, 42, and 84 dry Mg ha' 1 on the poorly-drained Acredale soil. Rates of 0, 42, 84, 126, 168, and 210 dry Mg ha'1 were applied on the well-drained Bojac, Davidson, and Groseclose soils. The 210 dry Mg haâ 1 sludge rate supplied 3300 and 6600 kg of N and P haâ 1, respectively. A 14-day anaerobic N incubation study indicated that mirreralization varied from approximately nine to four percent of sludge N from the 42 to 210 Mg haâ 1 application rates, respectively. Sludge application increased N uptake (rz = 0.98** to 0.99**) by the 1984 com grown on the three well-drained soils. Nitrogen balance data indicated that quantities of unrecovered N ranged from six to 21 percent where sludge was applied.
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    Biological and Chemical Renovation of Wastewater with a Soil Infiltrator Low-Pressure Distribution System
    DiPaola, Tracey Stickley (Virginia Tech, 1998-06-23)
    An alternative on-site wastewater treatment and disposal system (OSWTDS) consisting of a soil infiltrator with low pressure distribution was evaluated in a soil that was unsuitable for a conventional OSWTDS under current Commonwealth of Virginia Sewage Handling and Disposal Regulations, due to a shallow seasonally perched water table and low hydraulic conductivity. The absorption field consisted of two subsystems numbered as 1 and 2 with effluent design loading rates of 5.1 and 10.2 Lpd/m2, respectively (actual loading rates of 2.4 and 4.9 Lpd/m2, respectively). Soil matric potentials compared seasonally for each subsystem and indicated that both provided similar hydraulic performance. Background water quality was generally improved by subsurface movement through the absorption fields. A bacterial tracer was found in shallow (45.7 cm) and deep (213.4 cm) sampling wells within 24 h in the two subsystems (but in low numbers) over both summer and winter sampling periods. A viral tracer was detected within 48 h in both shallow and deep wells, but only in subsystem 2 in the winter. In evaluating denitrification potential, the addition of glucose to soil core samples did increase quantitatively, although not significantly, nitrous oxide production in each subsystem, at each depth, during each season. Overall, the performance of both subsystems was very similar. The soil infiltrator functioned very well, as designed for the site and soil limitations. It appears to be a potential alternative OSWTDS for use in problem soils.
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    Carbon and nitrogen dynamics on a forest site receiving continual papermill sludge applications: a soil column study
    Duncan, Carla S. (Virginia Tech, 1992-12-15)
    Successful renovation of wastewater and sludge via land application depends upon sludge-induced soil changes associated with carbon (C) and nitrogen (N) cycles within the soil/plant system. The C, N, and hydrologic cycles within a soil/sludge system receiving a year-round, daily application of paper mill sludge were studied. Soil samples were collected from three locations on a land application site in the Piedmont of Virginia that had received papermill sludge applications for six, two, and no prior years. The average application rate was 4.4 cm/wk, each week of the year, with a N loading of 700 kg N ha⁻¹yr-⁻¹. The column study showed that C and N were still accumulating on the land application site after 6 years, but at a decreasing rate. Based on this study, C accumulation will level out after 13 years of application, but N will continue to accumulate for almost 30 years. As application period increased, soil bulk density increased in the O, A, and B horizons, the percentage of non-capillary porosity fell below 10% in the A horizon and approached zero in the B horizon, and there was a dramatic decrease in the soil's hydraulic conductivity in both the A and B horizons. Nitrogen leaching is expected to increase with time due to high amounts of N in the papermill sludge, a continued narrowing of the C:N ratio, a high percentage of nitrification, and low denitrification rates. Experimental timing and rates of sludge additions were imposed to alter the aerobic/anaerobic properties of the soil system to determine the conditions under which optimum C and N mineralization, nitrification, and denitrification would occur. Application rates were factorially arranged for single or multiple doses on a daily or alternating schedule. The C decomposition and N mineralization processes were both optimized with an increase in the length of cycle; they were maximized with an alternating 9 days on/9 off application schedule. The nitrification potential also increased with the length of cycling, with an average nitrification rate of 96%. Denitrification was minimal in all treatments, with an average denitrification rate of 16%. This was primarily attributed to movement of nitrate-N below the most biologically active zone in the soil column. Sludge renovation will ultimately depend upon the excess N being sequestered in plant biomass or denitrified. Proper management of these processes will ensure that wastes decompose, and that N is stored or evolved as a benign gas rather than leached at unacceptable levels.
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    A computer simulation model for investigating the effect of land application of sludge on runoff water quality
    Deizman, Marcia McCutchan (Virginia Tech, 1989-04-22)
    CREAMS-NT, a modified version of the field-scale model for Chemicals, Runoff, and Erosion from Agricultural Management Systems (CREAMS) model, was developed to simulate the nitrogen (N) transformations and subsequent nutrient transport processes which occur in the soil following organic waste applications. CREAMS-NT accounts for nutrient addition through fertilization and rainfall and losses of N by volatilization, denitrification, plant uptake, leaching, and overland flow. Data required by CREAMS-NT includes runoff volume, sediment yield, percolation, and soil environmental conditions which is generated by the hydrologic and erosion components of the original CREAMS model. The mineralization, nitrification, denitrification, ar1d volatilization processes are simulated using firstâ order knetic equations adjusted for the effects of soil environmental conditions including temperature, moisture, pH, soil/sludge contact, and soil cation exchange capacity. Prior to a runoff event, soil ammnonium-N (NH4 â N) is partitioned between adsorbed and desorbed phases. CREAMS-NT predicts the transport of organic-N, NH4 â N, and sediment=bound phosphorus (P3b) in runoff using enrichment ratios. The transport of soluble nutrients, nitrate-N (NO3 â N), NH4 â N, and soluble P (PTF), is estimated using extraction coefficients.
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    Control of Volatile Organic Compound (VOC) Air Pollutants
    Hunter, Paige Holt (Virginia Tech, 2000-06-01)
    A variety of methods exist to remove volatile organic compound (VOC) air pollutants from contaminated gas streams. As regulatory and public opinion pressures increase, companies are searching for more effective methods to control these emissions. This document is intended as a guide to help determine if existing systems are adequate and to provide additional information to improve the efficiency of the systems. It explores conventional methods of controlling VOC emissions, as well as innovative technologies including membrane separation, plasma destruction, and ozone catalytic oxidation. The conventional technologies covered include condensation, adsorption, absorption (or scrubbing), thermal incineration, flaring, catalytic incineration, and biofiltration. Each chapter includes a description of the technology, a discussion of the types of systems available, notes on the design of the system, economic estimates, an explanation of potential problems, and a list of considerations for installation and maintenance concerns. The final chapter is dedicated to the preparation and characterization of metal catalysts which were developed to improve the reaction rate of VOCs using ozone as an oxidant.
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    Denitrification in low pressure distribution onsite wastewater disposal systems
    Degen, Marcia J. (Virginia Tech, 1992-12-05)
    The effects of effluent type, effluent loading rate, dosing interval, and temperature on denitrification in low pressure distribution, on-site wastewater treatment and disposal systems (OSWTDS) were evaluated in this study. The treatments were surface and subsurface soil horizons; nitrified and non-nitrified wastewaters; 0.5, 1.0, and 1.5 times the Virginia Department of Health (VDH 1989) recommended wastewater loading rate; 24 and 48 hour dosing intervals; and summer and winter temperatures. Surface and subsurface soil cores were collected from a Groseclose silt loam soil (clayey, mixed, mesic Typic Hapludult) and subjected to the various treatments. The effects of the treatments on denitrification were evaluated based on analyses of leachate from the cores, soil chemical analyses, and microcosm studies to estimate actual denitrification activity. A model was developed from the study that estimated the mean N₂O production for each combination of experimental treatments. The results of the study and the model indicate that denitrification can be enhanced in OSWTDS by the application of non-nitrified wastewater at one-half the VDH recommended loading rate, or 1.25 cm/day, for surface soil horizons (30 min inch⁻¹ percolation rate) using a 48 hour dosing interval. A field study was conducted on a Lowell silt loam soil (fine, mixed, mesic Typic Hapludalf). Denitrification was measured at this site using acetylene blocking and the results compared to those predicted by the denitrification model developed from the laboratory data. The field measurements of denitrification based on N₂O concentration in the soil atmosphere were three orders of magnitude higher than that predicted by the model. It was concluded that the laboratory techniques can be used to determine optimum method of operation for denitrification in a low pressure distribution system, but it cannot be used to determine the field design loading rates.
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    Determining Sources of Fecal Contamination in Two Rivers of Northumberland County, Virginia
    Szeles, Cheryl Lynne (Virginia Tech, 2003-04-09)
    The goal of monitoring the water quality of shellfish beds is to provide protection against transmission of water-borne infectious diseases. The Coan River and the Little Wicomico River contain shellfish beds that are closed to harvest due to contamination with fecal bacteria. These two rivers are located in Northumberland County, Virginia, and empty into the lower Potomac River and the Chesapeake Bay. Bacterial source tracking (antibiotic resistance analysis of Eschericia coli) was used to determine the sources of fecal contamination that have caused shellfish harvest closures in these two rivers. A total of 1,248 Eschericia coli isolates were collected from known sources to build a regional library for the rivers. The Virginia Department of Shellfish Sanitation (DSS) and project cooperators collected known source samples from August 2001 to September 2002. The Average Rate of Correct Classification for the known source library was 71.9%, with a total of 930 isolates correctly classified. The categories (and rates of correct classification) were Birds (84.7%), Humans (74.8%), Livestock (72.4%), Pets (62.0%), and Wildlife (65.7%). The library was used to identify the sources of Eschericia coli isolated from DSS sampling stations along the Coan and Little Wicomico Rivers from August 2001 to September 2002. Some stations contained a substantial human signature, while wildlife and birds are also major contributors. The results will be used to decide the necessary changes that need to be addressed if the shellfish harvesting beds are to be reopened.
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    Determining Sources of Fecal Pollution in the Blackwater River Watershed, Franklin County, Virginia
    Bowman, Amy Marie (Virginia Tech, 2001-08-02)
    Antibiotic resistance analysis (ARA) was used to determine sources of fecal pollution in the Blackwater River in South-central Virginia. The Department of Environmental Quality designated six segments as impaired due to high fecal coliform concentrations with non-point source (NPS) agriculture the suspected source of impairment. The Blackwater River watershed encompasses 72,000 ha of dairy, beef, and intensive production agriculture, abundant wildlife populations and many homes with onsite septic systems. A library of antibiotic resistance profiles based on 30 concentrations of 9 antibiotics was developed for 1,451 enterococci isolates from human, cattle, chicken, horse, goat, sheep, deer, raccoon, muskrat, goose, duck, coyote, and wild turkey fecal samples. Each isolate was classified as human, wildlife or livestock. Correct classification rates were 82.3% for human, 86.2% for livestock and 87.4% for wildlife isolates when profiles were analyzed with discriminant analysis. Profiles were also determined for 48 isolates from 128 stream samples collected periodically from August 1999 thru April 2001 and compared to the known sources using discriminate analysis. A human signature was found at each site at least once during the year, ranging from 0.0% to 85.0% of the sample isolates. The livestock signature varied from 2.3% to 100% over sites and months, and the wildlife signature varied from 0.0% to 79.5%. The results indicate that both humans and wildlife contribute to fecal pollution in addition to the suspected source, livestock, and reducing fecal pollution will require consideration of all three sources. The results from this research are being used to develop a total maximum daily load (TMDL) project allocations for fecal coliforms in the Blackwater River. Isolates identified by ARA were also profiled using the Biolog metabolic identification system. A library of metabolic profiles was constructed from known source isolates. Stream isolates were identified by Biolog and the metabolic profile was compared to the Biolog library. Of ten stream isolates identified by ARA as human, the Biolog library identified one as human, four as livestock, and five as wildlife. Of ten isolates identified by ARA as livestock, the Biolog library identified seven as livestock and three as wildlife. Of ten isolates identified by ARA as wildlife, one was identified as human, three as livestock and six as wildlife. The overall correct classification of Blackwater isolates in the Biolog library was 14 of 30 isolates, or 47%. Although the Biolog library was constructed with some isolates from the Blackwater basin, there may not be enough isolates in the Biolog library to adequately represent the variability shown by the Blackwater isolates, resulting in lower than expected correct classifications. In spite of these results, Biolog remains promising as one of several tools with potential as a bacterial source tracking method.
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    Determining Sources of Fecal Pollution in Water for a Rural Virginia Community
    Graves, Alexandria Kristen (Virginia Tech, 2000-08-01)
    This project involves developing and applying bacterial source tracking (BST) methodology to determine sources of fecal pollution in water for a rural community (Millwood, VA). Antibiotic resistance analysis (ARA) is the primary BST method for fecal source identification, followed by randomly amplified polymorphic DNA (RAPD) analysis for confirmation. Millwood consists of 66 homes, all served by individual septic systems, and a stream (Spout Run) passes through the center of the community. Spout Run drains a 5,800 ha karst topography watershed that includes large populations of livestock and wildlife. Stream and well samples were collected monthly and analyzed for fecal coliforms and fecal streptococci, starting in 5/99 and ending in 5/00. Twelve percent of the well samples and 92% of the stream samples were positive for fecal coliforms, and 26% of the stream samples exceeded the recreational water standard (1,000 fecal coliforms/100 ml). ARA of fecal streptococci recovered from the stream samples indicated that isolates of human origin appeared throughout the stream as the stream passed through Millwood with a yearly average of (approx. 10% human, 30% wildlife, and 63% livestock), and the percent human origin isolates declined downstream from Millwood. These results were obtained by comparing the antibiotic resistance profiles of stream isolates against a library of 1,174 known source isolates with correct classification rates of 94.6% for human isolates, 93.7% for livestock isolates, and 87.8% for wildlife isolates. There is a human signature in Spout Run, but it is small compared to the proportion of isolates from livestock and wildlife. The sporadic instances where well water samples were positive appeared primarily during very dry periods. Restricting livestock access to streams can dramatically lower fecal coliform counts during the unusually hot and dry periods. Reducing FC counts to below recreational water standards for Virginia (1000 per 100ml for any one sample) may be achievable, however to maintain streams below standards may prove to be difficult, as Spout Run is in an area where there are large populations of Canada geese, deer, and other wildlife, and will be hard to restrict these animals.
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    Development and evaluation of a colorimetric coliphage assay detection system
    Ijzerman, M. Marian (Virginia Tech, 1993-07-14)
    A Colorimetric Coliphage Assay Detection System (CCADS) that is composed of a Liquid Colorimetric Presence-Absence (LCPA) method and a Colorimetric Agar-Based (CAB) method was developed to overcome the limitations imposed by the Standard Methods for the Examination of Water and Wastewater agar-based coliphage method (APHA method). Both CCADS methods are based on the induction of β-galactosidase in Escherichia coli and the release of the enzyme through a lytic cell infection. The released enzyme then cleaves a chromogenic substrate which produces a colored reaction product. The CCADS was evaluated against the APHA method under laboratory conditions using a common sewage coliphage strain as a model (American Type Culture Collection- 13706-B2), and under field conditions using water samples collected from four different sources. During the laboratory evaluation, both the LCPA and CAB methods were found to be superior in coliphage detection to the APHA method because: 1) the LCPA and CAB methods were easier to read and interpret than the APHA method, 2) the LCPA and CAB methods were not subject to false positive results, 3) the LCPA method theoretically detected fewer coliphage particles than the APHA method, and 4) the CAB method detected roughly twice the number of coliphage particles than the APHA method. During the field evaluation, the results indicated: 1) the LCP A method was as reliable as either the CAB or APHA methods in coliphage detection, 2) the LCP A and CAB methods were easier to read and interpret than the APHA method, 3) neither the LCPA method nor the CAB method were subject to false positive results, 4) the CAB method detected more coliphages than the APHA method under conditions of high fecal pollution, but both methods performed equally well in coliphage detection under conditions of low fecal contamination, and 5) the LCPA and CAB methods were equally as sensitive in coliphage detection as the APHA method. Finally, the coliphage group proved to be a useful indicator of fecal pollution in nonpotable water supplies that exhibited a high degree of fecal pollution, whereas they were not shown to be useful indicators in potable water supplies that exhibited low levels of fecal contamination. The lack of coliphage detection sensitivity under conditions of low fecal contamination does not appear to be method limited, but rather the result of inefficiencies in processing environmental samples using the concentration methods currently available.
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    Development of field-specific spring N rate recommendations for winter wheat
    Scharf, Peter C. (Virginia Tech, 1993)
    Optimum spring N fertilizer rates for winter wheat in Virginia vary widely from field to field, but traditionally spring N is applied at a uniform rate to all fields. A recently-developed tissue test procedure provides a field-specific evaluation of crop N status and predicts optimum N rate for the second spring N application in a split spring application management system. However, this procedure is based on a small number of researcher-planted experiments utilizing a single cultivar; it fails to provide field-specific rate recommendations for the first spring N application; and it is not accessible to farmers who are unwilling to split their spring N applications. Our objectives were: to evaluate the reliability of the tissue test procedure in a large number of farmer fields; to develop a method for making field-specific N rate recommendations for the first spring application in a split-application management system; and to develop a method for making field-specific N rate recommendations in a single-application management system. Forty-five spring N rate experiments were established in farmer fields over a five-year period. A range of N fertilizer rates was applied in early spring (Zadoks growth stage 25) and again in mid-spring (Zadoks growth stage 30) in all possible combinations. Yield data were used to calculate economic optimum N rates at growth stage (GS) 25 and GS 30 with split-application management, and at GS 25 with single-application management. These optima were regressed against a variety of predictor variables measured in the same fields. The reliability of the previously-developed tissue test procedure for making GS 30 N rate recommendations was confirmed. Tiller density was the best predictor of optimum GS 25 N rate with split-application management, while soil nitrate to 90 cm was the best predictor of optimum GS 25 N rate with single-application management. These three relationships fit together to form a flexible and powerful system for making spring N rate recommendations for winter wheat. This system increased estimated profit and apparent fertilizer efficiency in these experiments.
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    The effect of distance between artificial drainage facilities and disposal trenches on the movement of biological and chemical pollutants from septic tank effluent
    Stewart, Larry Wayne (Virginia Polytechnic Institute and State University, 1982)
    A field study was conducted at a residence in Chesapeake, Virginia to determine the effect of setback distances from a drainage ditch on the disposal of septic tank effluent. The study was done from September 1979 to August 1981. The soil used is the Tomotley series belonging to the fine-loamy, mixed, thermic family of Typic Ochraquults. Four prototype trenches were installed at 1.5, 3, 6 and 21 m from the edge of a drainage ditch which was 1.5 m deep. The trenches were pressure dosed equally with 2.4 to 4 cm per day. Replicated nests of sampling wells at depths 90, 150 and 300 cm were placed with distance from the trenches. Continuous stage recorders were positioned 4.5, 29.1 and 60 m from the ditch to monitor water table behavior. Groundwater analysis included fecal coliforms, the NH₄, NO₃, NO₂, Na, Ca, Mg, Cl and PO₄ ions, pH and EC. Ammonium concentrations in the soil beneath the trenches indicated nonuniform effluent infiltration yet more uniform than with conventional gravity flow distribution. High sodium absorption ratios of the septic tank effluent ranging from 18 to 45 did not significantly reduce infiltration rates as no ponding of effluent in the trenches was observed. The existing land surface was sloped greater than the water table gradient resulting in decreasing unsaturated depths with closeness to the ditch. The mean distances between the trench bottom and the water table were 64 cm at 3 m, 80.1 at 6 m and 90.4 cm at 21 m. The accumulation of fecal coliforms, NH₄, P, Cl and total salts (EC) in the groundwaters at 120 to 150 cm depth was inversely proportional to the mean distances from the trench bottoms to the water table. The lack of denitrification occurring underneath the trench with the most extensive unsaturated zone suggests NO₃ may accumulate under disposal systems that have mean unsaturated depths of ≥ 90 cm. Effluent movement was mainly lateral and in the upper zone of the water table with limited vertical movement below the water table surface. An equation applying D-F theory to infinitely deep soil was developed to describe flow for the given drainage system and for the inclusion of standard size drain fields. The current practical setback distance of 21 m is considered counterproductive for effluent treatment for some situations.
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    Effect of sulphur fertilization on growth and chemical composition of sorghum (Sorghum Bicolor L.) and on utilization of sorghum silage fed to wethers
    Ahmad, Muhammad Rashid (Virginia Tech, 1991-05-24)
    Sulphur (S) is an essential element for plant and animal nutrition, but widespread deficiencies of S occur world wide. Current recommendations for nitrogen (N):S ratios are 15 to 18:1 and 10 to 12:1 for plant and animal nutrition, respectively; but recent information suggests these may not predict animal response. Sorghum is an important crop, particularly in drier climatic regions but little is known concerning S-nutrition for sorghum growth or utilization of S-fertilized forages. Sorghum "Pioneer 947" was grown on a Lucy loamy sand (loamy, siliceous, thermic Arenic Kandiudult) in King William County, VA, with and without S fertilization (0 vs. 138 kg S ha⁻¹ as ammonium sulphate) in a randomized block design with four replications. Sulphur fertilization decreased (P < 0.05) soil pH and increased soil S in the 0 to 25 cm (P < 0.08) and 25 to 50 cm (P < 0.05) soil layers. An increase in Mehlich-I extractable soil P, Mn (P < 0.05) and soil N0₃-N (P < 0.06) at surface 25 cm layer occurred with S-fertilization. At harvest, S-fertilization increased (P < 0.05) S and water soluble carbohydrates and decreased (P < 0.05) N:S ratio and P concentration in whole plants. Sorghum leaves were higher (P < 0.05) in N, S, Ca, Mn and Cu in S fertilized compared to non-S fertilized sorghum. Sulphur fertilization decreased (P < 0.05) concentration of hydrocyanic acid (HCN) in the upper three leaves. A greenhouse experiment was conducted with the Lucy soil and 'Pioneer 947' sorghum to further investigate effects of fertilization (0, 70, and 140 kg S ha ⁻¹) as ammonium sulphate in a completely randomized design with five replications. Sulphur application decreased soil pH, and extractable soil K linearly (P < 0.01), and increased extractable soil S linearly (P < 0.01).
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    Effects of Feeding Phytase Enzyme and HAP Corn on Solubility of Phosphorus, Copper, and Zinc in Turkey Manure and Manure-Amended Soils
    Lawrence, Christophe L. (Virginia Tech, 2000-04-28)
    Manure from turkey poults on five diets were extracted both fresh (wet) and after drying. Soils amended with wet manure were also extracted. Phosphorus, Cu, and Zn were extracted with 0.01 M CaCl₂ and acidic Mehlich III extractant (Zn in soil extracts was not evaluated). Dietary treatments were (1) normal phytic acid (NPA) corn and 0.135% inorganic P (NPA diet); (2) NPA corn, 600 units phytase enzyme, and 0.135% inorganic P (NPA+Phyt diet); (3) High available phosphorus (HAP) corn and 0.135% inorganic P (HAP diet); (4) HAP corn, 600 units phytase, and 0.135% inorganic P (HAP+Phyt diet); (5) NPA corn and 0.345% inorganic P (NPA+P diet). The NPA+P diet was similar to conventional diets being fed commercially. The NPA+Phyt diet was similar to alternative, phytase-amended diets being fed commercially. Feeding the alternative NPA+Phyt, HAP, and HAP+Phyt diets instead of the NPA+P diet reduced total P in manures by 40%, but increased the percentage of total manure P extracted with 0.01 M CaCl₂ from fresh excreta (P < 0.05). Soils amended with wet NPA+Phyt, HAP, and HAP+Phyt manures released 29 to 49% more water-soluble P than soils amended with NPA+P manure on an equal-P basis (P < 0.05). Feeding the NPA+Phyt diet instead of the NPA+P diet did not affect the percentage of total P manure extracted by Mehlich III from wet excreta, while feeding the HAP and HAP+Phyt diets increased the percentage of total manure P soluble in Mehlich III (P < 0.05). Soils amended with wet NPA+Phyt manure did not release more Mehlich III-extractable P than soils amended with NPA+P manure on an equal-P basis. Soils amended with wet HAP and HAP+Phyt manures released more Mehlich III-extractable P than soils amended with NPA+P manure on an equal-P basis (P < 0.05). Treatment-induced differences in extractability of manure and soil P appeared to be caused by a higher proportion of P in calcium phosphate form in the NPA+P manure. Drying manures prior to extraction generally heightened differences in solubility of P between the NPA+P and other manures. Feeding the alternative NPA+Phyt, HAP, and HAP+Phyt diets instead of the NPA+P diet did not affect total Cu levels in manure or the percentage of total Cu extracted from manure with 0.01 M CaCl₂. After soils were treated with manure on an equal-Cu and equal-N basis, soils amended with NPA+Phyt, HAP, and HAP+Phyt manures released more water-soluble Cu than NPA+P-amended soils (P < 0.05). Under P-based manure management, soils amended with the three alternative manures released 92 to 108% more water-soluble Cu than NPA+P-treated soils (P < 0.05). Extractable Cu increased so dramatically because conversion to the alternative diets boosted total manure loadings by 67%. Mehlich III extraction of soils amended with manure on an equal-N and -Cu basis indicated no effect of manure type on Cu availability. Feeding the NPA+Phyt, HAP, and HAP+Phyt diets instead of the NPA+P diet did not affect total Zn levels in excreta, but caused at least a five-fold increase in the percentage of total manure Zn extracted by 0.01 M CaCl₂ from fresh excreta (P < 0.05). Feeding the NPA+Phyt, HAP, and HAP+Phyt diets did not alter the percentage of total manure Zn extracted by Mehlich III from wet excreta.
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    Effects of hydraulic loading and laundry detergent on the operation of aerobic package treatment systems
    Hanna, K. Michael (Virginia Tech, 1993-05-05)
    This study focused on three potential problems with the operation of aerobic package treatment systems: hydraulic retention time, laundry detergents, and hydraulic surges. To determine the effect of hydraulic retention time on system performance, six bench scale activated sludge systems were constructed. Wastewater from an actual residence was collected twice per week and fed to the small activated sludge systems. Two of the systems had a hydraulic retention time of 2 days, two had a hydraulic retention time of 1 day and two had a hydraulic retention time of 0.5 days. Effluent quality was stable and good with regard to chemical oxygen demand (COD) and ammonia (NH)-N) and seemed to be independent of hydraulic retention time. All of the systems performed well, despite considerable variability in influent strength. To study the effect of high concentrations of laundry detergents on the operation of package treatment systems, three of the six laboratory systems were fed high concentrations of detergent. Other than some residual COD from the detergent, no effect on system performance was observed. The final component of the study was the modification of an existing package treatment system to equalize flows from an automatic washing machine. After a month of operation the modified system produced a more constant effluent quality, than did the unmodified system. The field system, with and without modification, had a low mixed liquor suspended solids (MLSS) concentration (35 mg/L). This was probably the result of the long hydraulic retention time. As a result of the low MLSS the system, with and without modification, did not meet Virginia effluent requirements for BODs, TSS or D.O. or generally accepted levels of NH₃-N.
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    Effects of Reduced Early Post-Sprigging Nitrogen Application on Bermudagrass Sprig Establishment
    Zalewski, Jon Eric (Virginia Tech, 2000-07-24)
    Nitrate contamination of ground and surface waters is of serious concern in the United States. Since nitrate is considered one of the most widespread groundwater contaminants, research continues in many disciplines to identify and mediate possible sources (Petrovic, 1990). An opportunity to evaluate a possible source of nitrate contamination exists during bermudagrass sprig establishment. Since most "improved" bermudagrass varieties are established vegetatively, due to lack of viable seed, turf managers apply large quantities of soluble urea weekly to push growth. During this grow-in, turf managers typically apply 48.8 soluble kg N ha-1 wk-1 for an eight to ten week period. We hypothesize that the quantity of nitrogen applied is in excess and that similar 8 to 10 week grow-in can be achieved with less nitrogen especially during the first 4 weeks when there are few plants per unit area. Three interrelated studies were conducted. A "field trial", consists of 1.8 m2 plots in 4 replications of 27 different nitrogen rates ranging from 4.9 kg N ha-1 wk-1 to 48.8 kg N ha-1 wk-1. A lysimeter study quantified leaching nitrate loss using the same weekly nitrogen rates, however, only six treatments existed. All plots were rated at weeks 4, 8 and 10 for cover, color, and density. A greenhouse study was implemented to evaluate potential nitrogen use for a single bermudagrass sprig, during the early post-sprigging stage. In 1998 and 1999, it appears that typical weekly nitrogen rates of 48.8 kg N ha-1 are in excess. Similar results were found using 48.8 kg N ha-1 to 97.6 kg N ha-1 over the first four week period and 195.2 kg N ha-1 to 244.0 kg N ha-1 during the entire grow-in. A 25 to 50 percent reduction in nitrogen application when compared to the typical 390.4 kg N ha-1. Lysimeter results revealed large quantities of nitrate lost via leaching. The 390.4 kg N ha-1 lost 34.7 and 44.6 percent of applied nitrogen in 1998 and 1999, respectively. Furthermore, similar turfgrass cover, color, and density were achieved using 80 percent less nitrogen during the grow-in period on sand-based media. The greenhouse study suggests that during the early post-sprigging period individual sprigs do not require large quantities of soluble nitrogen even on sand-based media. Results indicated that individual sprigs did not utilize 48.8 kg N ha-1 wk-1 during early post-sprigging. Similar results with respect to shoot weight, shoot length, and root weight were found using 40 percent less applied nitrogen. However, greater nitrogen rates may be necessary as plant density and root development increase later in the establishment period.
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    Effects of soil texture, soil depth, and treatment on septic tank effluent renovation
    Keeling, William G. (Virginia Tech, 1995-12-05)
    This study compared the effects of soil texture, soil depth, and additional treatment, by constructed wetland (CW) and recirculating sand filter (RSF) systems, on wastewater renovation in a texture group 2 (loam) and a texture group 3 (clay loam) soil. The soils with depths of 15, 30, and 45 cm were placed in the columns with a Gidding's hydraulic soil probe in order to retain the soils structure in situ. The texture group 2 columns were dosed with septic tank eflluent (STE), constructed wetland effluent (eWE), and recirculating sand filter effluent (RSFE) at 685 cm³ per day and the texture group 3 columns were dosed at 670 cm³ per day with the same effluents. These dosing events were split into 2 separate (12 h) events. The leachate from both groups of soil columns were analyzed for fecal coliforms (FC), biochemical oxygen demand (BODs), ammonium (NH₄-N), nitrate (NO₃-N), phosphate (PO₄-P), pH, total dissolved solids (TDS), electrical conductivity (EC), and chloride. In the texture group 2 soil the reduction in fecal coliform numbers was 88% and 99%, respectively, for the CW and the RSF and, in the texture group 3 soil was 91% and 99%, respectively, for the CW and the RSF. There was a reduction in BODs concentrations of 32% and 69% ,respectively, for the CW and the RSF. There was a 42% and 84% decrease in NH₄ concentrations, respectively, for the CW and the RSF. These reductions show that treatment of STE by CW or RSF can be substituted for soil depth in texture group 2 and 3 soils and will improve drainfield performance. Texture group 2 soils are less effective at STE renovation than texture group 3 soils at all soil depths. This was evidenced by higher FC counts and concentrations of BOD, N, and P in the leachates from these columns.
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    Environmental and agronomic aspects of municipal solid waste heavy fraction used for turfgrass production
    Flanagan, Mark Steven (Virginia Tech, 1991-01-15)
    Disposal of municipal solid waste has become a tremendous problem in the United States. To reduce the volume of garbage that requires deposition in landfills, innovative methods of recycling need to be investigated. Several experiments were conducted in Blacksburg, Virginia, to evaluate the use of heavy fraction, a by-product of a solid waste separation process, as a soil amendment for production of turfgrass sod. In a field plot experiment using Kentucky bluegrass (Poa pratensis L.), measurements of sod strength taken 8.5 and 9.5 months after seeding were greater for sod grown in topsoil amended with heavy fraction than for turf grown in topsoil only. These results imply that the use of this by-product for turfgrass production may reduce the time required to produce a harvestable sod. In a container study, physical properties of a loam topsoil were altered 16 months after addition of heavy fraction. Bulk density and particle density were reduced and organic matter content increased by soil incorporation of this by-product. Total porosity and air porosity (macropore space) of the topsoil increased whereas water porosity (micropore space) decreased with increasing amount of applied heavy fraction. Soil fertility was enhanced and soil pH raised by addition of heavy fraction. Concentrations of extractable NH₄ -N, P, K, Ca, Mg, Mn, and Zn in soil were increased by the application of heavy fraction, as were concentrations of K, Ca, S, Mg, and Mn in leachate collected in lysimeter studies. Improved fertility resulted in greater aesthetic quality, clipping yields, and tissue N content for tall fescue (Festuca arundinacea Schreb.). Lysimeter studies indicated that the greatest environmental concern associated with the use of heavy fraction for turfgrass production appears to be the potential for leaching of N0₃-N during turf establishment. With loading rates of 414,747 kg ha⁻¹ or lower, however, the amount of N0₃-N leached from heavy fraction-amended topsoil was no greater than that leached from topsoil containing no heavy fraction. Concentrations of N0₃-N in leachate for all loading rates of heavy fraction decreased to levels well below 10.0 mg L ⁻¹ approximately two months after sodding the lysimeters with tall fescue. Leachate analyses indicated minimum potential for P or heavy metal contamination of groundwater from heavy fraction.