Browsing by Author "Baker, James C."

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    Agronomy Handbook
    Brann, Daniel Edward; Abaye, Azenegashe Ozzie; Peterson, Paul R.; Chalmers, David R.; Whitt, David L.; Chappell, Glenn F.; Herbert, D. Ames Jr.; McNeill, Sam; Baker, James C.; Donohue, Stephen J.; Alley, Marcus M.; Evanylo, Gregory K.; Mullins, Gregory L.; Hagood, Edward Scott; Stallings, Charles C.; Umberger, Steven H.; Swann, Charles W.; Reed, David T.; Holshouser, David L. (Virginia Cooperative Extension, 2009-05-01)
    Provides readers with a source of agronomic information such as field crops, turfgrasses, variety selection, seed science, soil management, nutrient management and soil suitability for urban purposes that does not change frequently - pesticide and varietal information changes frequently and is therefor not included.
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    An Analysis of Palustrine Mitigation Wetlands in the Virginia Coastal Plain
    Cummings, Angela R. (Virginia Tech, 1999-05-13)
    In recent years, the success of wetland mitigation projects and their ability to function as natural systems has been questioned. This study was conducted (i) to characterize and examine differences between mitigation and natural wetlands, (ii) to examine differences in soil morphology along a wetness gradient in mitigation and natural wetlands, and (iii) to observe changes in mitigation wetlands with time. Site characteristics, including soil properties, hydrology, and vegetation, were analyzed for three mitigation-reference wetland pairs located in the Virginia Coastal Plain. Hydrologic regimes of mitigation areas, when compared to reference areas, generally showed larger differentials between seasonal high and low watertables. Mitigation areas, dominated by herbaceous vegetation, tended to be lower in C and N levels and higher in soil pH, and much higher in bulk density than the mature forested reference wetland. Initially low levels of C and N did not increase significantly over the five-year study period. Soils in the mitigation area were more uniform and considerably less differentiated when compared to those of the reference area. Testing for Fe(II) with alpha-alpha, dipyridyl dye solution produced mixed results, obtaining both positive and negative reactions to saturated samples. Oxidized rhizospheres, associated with active root channels in surface horizons, formed in less than ten years under the current hydrologic conditions. These features were more abundant and more prominent in areas saturated at or above the surface for longer periods of time. Overall, site differences between mitigation and reference areas are mainly due to construction practices and a lack of organic matter accumulation. Better design methods should incorporate the addition of organic amendments, with attempts to minimize soil compaction.
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    An approach to studying soil-landscape relationships in Virginia
    Stolt, Mark H. (Virginia Tech, 1990)
    Various methods and techniques were used to examine soil-landscape relationships for residual and colluvial soils of Virginia. Soil micromorphology indicated that although some BC and C horizons in the field appeared structureless, evidence of pedogenic process was observed. These were designated as either BCt, BC, or CB horizons depending on the amount of oriented clay and the rates of change with depth of clay, DCB extractable Fe, and sand contents. Soil variability was examined for the overall study, as well as within toposequences, pedons, and individual horizons. Most of the overall variability was attributed to differences between study sites or between horizons, with minimal amounts due to landscape position. Substantial lateral variability occurred within horizons indicating a strong need for subsampling within horizons of the same pedon. Lithologic discontinuities were found to be difficult to recognize without obvious field evidence. Reconstruction analysis was used to examine soil and saprolite formation. Summit and backslope soils were found to be essentially the same in both morphology and degree of profile development. Sand weathering and clay eluviation/illuviation were the major soil forming processes occurring within these soils. Footslope soils were less developed than associated summit and backslope soils, with both depositional and pedologic processes contributing to soil formation and development. Thickness of saprolite was found to decrease. from the summit to the footslope. Thicker saprolite at the summit was apparently related to the greater stability of the summit position compared to the backslope and footslopes. A bucket auger was modified to obtain undisturbed samples of deep saprolite for reconstruction analysis. Saprolite reconstruction indicated that between 20 and 36 % of the mass of the partially weathered rock, which is the precursor to saprolite, is lost during saprolite formation. Most of these losses were either Al or Si. Initial soil formation was shown to occur at a faster rate than saprolite formation, but after substantial profile development, soil formation is reduced to a rate below that of saprolite formation, and saprolite accumulates below the solum. Reconstruction analysis was found to be a valuable tool in studying soil-landscape relationships.
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    Availability and distribution of copper in soils following eight annual applications of CuSO₄ or Cu-enriched swine manure
    Payne, Grover Garry (Virginia Polytechnic Institute and State University, 1986)
    Three field studies were established in 1978 and continued through 1985 in order to determine the effects of long-term Cu applications, as either CuSO₄ or Cu-enriched swine manure, at high application rates on corn (Zea mays L.) production. The studies were conducted on Bertie fine sandy loam (Aquic Hapludult), Guernsey silt loam (Aquic Hapludalf), and Starr clay loam (Fluventic Dystrochrept)-Dyke clay (Typic Rhodudult) soils in the Coastal Plain, Ridge and Valley, and Piedmont physiographic regions of Virginia, respectively. A laboratory incubation study was also conducted using the same soils to determine the effects of soil pH on the changes in forms of soil Cu present over a 256-day period following addition of CuSO₄ or Cu-enriched swine manure. Application of 336 kg Cu ha⁻¹ , as CuSO₄ , or up to 264 kg Cu, as Cu-enriched swine manure, from 1978 through 1985 had no adverse affects on corn grain yields or on Cu concentrations in corn ear leaves or grain. Copper concentrations in ear leaf tissue were increased only slightly (≤ 2.1 mg kg⁻¹) by the eight annual Cu additions with no increase in Cu content of grain being observed. Copper concentrations in both ear leaves and grain remained within normal levels. DTPA extractable Cu was linearly related to the cumulative amount of Cu applied to the three soils (r = 0.93 to 0.98, α= 0.01). Extractable soil Cu showed no relationship with Cu levels in grain or leaf tissue. Analysis of subsoil samples indicated little downward movement of the applied Cu due to leaching. Fractionation of the Cu in the three soils indicated increases in all fractions resulting from Cu treatments. Results of the laboratory incubation study showed that the distribution of applied Cu among soi 1 fractions was dependent on soil pH, length of time following Cu additions, and to some degree on the source of applied Cu. Levels of Ex-Cu and HOAc-Cu decreased with time and increasing pH. No consistent differences in Pyro-Cu were observed due to pH or length of incubation. Concentrations of Ox-Cu parallelled the levels of Fe and Mn in the soils and generally increased with time. Soils at low pH tended to contain less Ox-Cu than soils at higher pH levels.
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    Characterization and composition of selected Cecil map units in the Virginia Piedmont
    Thomas, Pamela J.; Baker, James C.; Simpson, Thomas W. (Virginia Agricultural Experiment Station, 1993-08)
    A study in Appomattox, Pittsylvania, and Lunenburg counties in the southern Piedmont of Virginia assessed composition and variability of a map unit named for a taxon of Typic Kanhapludults. Twelve delineations of Cecil sandy loam, 2 to 7 percent slopes, three to eight sites within each delineation, and three profiles within each site were randomly located in a two-level nested sampling scheme. Soil physical, chemical, and morphological data were collected from the Ap, Bt, and C horizons of each profile. In Appomattox County, 38 percent of the 81 profiles met the criteria for the Cecil soil series. An additional 33 percent of the profiles were taxonomically similar to Cecil. The remaining 29 percent were taxonomically dissimilar inclusions. In Pittsylvania County, 48 percent of the 75 profiles were Cecil series. An additional 47 percent of the profiles were taxonomically similar to Cecil. The remaining 5 percent were taxonomically dissimilar inclusions. In Lunenburg County, 42 percent of the 45 profiles were the Cecil series; the remaining 58 percent of the profiles were taxonomically similar to Cecil. Thus, the map unit in all three counties would be named Cecil and the map unit description in Appomattox and Pittsylvania counties would include dissimilar soils according to National Cooperative Soil Survey criteria. Taxonomic variability was reflected in the variability of taxonomically important soil properties. Percent base saturation decreased with depth in the profile. Maximum clay content occurred in the Bt horizon and ranged from 25 to 75 percent. The solum exhibited large variation in thickness. Subsoil properties important to classification (percent base saturation in the chemical control section, clay percentage in the particle-size control section, and solum thickness) exhibited considerable variation within delineations, but the variability was consistent from delineation to delineation. Intrusions of mafic material into the felsic crystalline system, from which Cecil and similar soils form, probably accounts for most of the variability in soil properties. Low plant available water, low bases, and high P-fixing capacity are major management concerns of the Cecil and similar soils. Understanding the interrelationship between map unit composition, variability, and soil properties is essential in increasing the productivity of these major landscape units.
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    Clay mineralogy and soil classification of alluvial and upland soils associated with Blackwater and Nottoway rivers in southeastern Virginia
    Al-Hawas, Ibrahim A. M. (Virginia Tech, 1989-10-06)
    Because the Coastal Plain of southeastern Virginia has not been extensively studied, thirty random samples associated with Blackwater and Nottoway rivers were collected in the spring of 1987 from Surry, Sussex, and Southampton counties. Soil classification as well as mineralogical, chemical, and physical analysis were conducted for all samples. The purposes of this investigation were to: (1)classify the soils in this area, (2) determine the distribution of sand and clay minerals, (3) examine the weathering effect on clay minerals on different position of the landscape for different parent material sources. The soils examined classified as follow: Aquic Hapludults 43% > Typic Hapludults 26.6% > Ultic Hapludalfs 10% > Humic Hapludults 3% = Typic Rhodudlts 3% = Aquic Hapludalfs 3% = Typic Udipsamment 3% = Typic Quartzpsamment 3% = Psammentic Hapludalfs. Qualitative analysis of clay minerals revealed that kaolinite and hydroxy interlayer vermiculite were the dominant clay minerals; that montmorillonite, mica, gibbsite quartz, and vermiculite were of lesser quantities; that chlorite, feldspar and interstratified minerals were of trace amounts. Kaolinite represents about 21-70%, HlV 11-60%, montmorillonite 0-20%, mica 0-16%, gibbsite 0-13%, quartz 1-12%, and vermiculite 0-10%. The presence of these minerals were mainly related to the acid reaction of the soil media, which was essentially attributed to Al and H ions in soil solution. From the past history and geological composition of the Piedmont it is assumed that kaolinitic minerals were transported and sedimented in the Coastal Plain. Hydroxy-interlayer vermiculite minerals was weathering from vermiculite because most of the Al was adsorbed by vermiculite to form HIV. Therfore, gibbsite was not precipitated. Montmorillonite was assumed to have formed from mica minerals. That was substantiated by statistical analysis which showed a high negative correlation between gibbsite and vermiculite (r=0.46, n=30) and between montmorillonite and mica (r=-0.6, n=10).
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    Cotton Yield as Related to Selected Physical and Chemical Properties of Soils of the Coastal Plain of Virginia and North Carolina
    Adcock, Clyde Wesley (Virginia Tech, 1998-08-28)
    Cotton (Gossipium hiristum, L) is a warm season perennial with indeterminant growth habit. In 1995, 42,500 and 300,000 hectares were grown in Virginia and North Carolina, respectively. Soil physical and chemical properties may limit cotton yields. The objective of this study was to; 1) determine influences of soil physical and chemical properties on yield, 2) validate existing preharvest yield estimators, and 3) determine the effect of subsoiling and/or subsurface liming on cotton development and root growth. Two hundred sites were sampled across the Coastal Plain of Virginia and North Carolina to a depth of 92 cm representing 5 major soil series. Soil samples were analyzed for selected physical and chemical properties from each horizon. Boll and plant counts were obtained while harvesting a 3-meter length of row at each site to determine yield for the 1996 and 1997 growing season. Cotton was grown in the greenhouse on 30 cm diameter cores of a soil with low subsoil pH and a hard pan to determine the effects of subsoiling and/or subsurface liming. Ninety days after planting, the cotton plants were harvested and the above ground biomass and rootmass were analyzed. Physical and chemical properties explained 52% of yield variability in 1996 and 27% in 1997. Physical and chemical properties that were significant to yield were surface bulk density, available water holding capacity, depth of the water table and Bt horizon, Mg, K, Ca, and Al content. Soil analysis for nutrient status at depths up to 45 cm were better indicators of cotton yield. Subsoiling with or without subsurface liming increased rooting depth over the untreated check. The subsurface liming reached first flower 11 days prior to the other treatments. The additional period for flowering and boll set in Virginia and North Carolina could increase potential yield.
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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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    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 Poultry Litter-Yard Waste Compost Application on Phosphorus Availability in Diverse Soils
    Mankolo, Regine Ndole (Virginia Tech, 1997-10-08)
    Land application of poultry litter has been successfully practiced for centuries to maintain and improve soil fertility, although over application may promote loss of nutrients through runoff or leaching. To decrease the potential for adverse environmental impacts of N and P in groundwater, a new approach developed in this research was to use a composted mixture of poultry litter (PL) and yard waste (YW) as a soil amendment for corn (Zea mays L.) production. Objectives of this research were to evaluate effects of pre-compost C:N substrate ratios for poultry litter-yard waste compost (PYC) on the availability of soil P, to determine the P response of corn plants to inorganic P, PL and PYC application, and to study relationships between P availability and both inorganic P and PYC application. Langmuir isotherms were used in this research to select soils with relatively high P fixation capacities. Phosphorus sorption maximum for soils evaluated were as follows: 304 and 449 micrograms of P per gram for A horizon Coastal Plain soils (Series: Kempsville and Myatt, respectively); 487 micrograms of P per gram for an A horizon Ridge and Valley soil (Series: Frederick); 918 and 603 micrograms of P per gram for A horizon Piedmont soils (Series: Elioak and Vance, respectively); 1099 microgram of P per gram for mine tailings (Series: Emporia located in the Coastal Plain); and 1524 microgram of P per gram for A and upper mixed horizon soil (Series: Starr from Piedmont region). Based on intermediate to high P sorption maxima, soil from the Vance and Starr series and mine tailing from Emporia series were selected for greenhouse research to evaluate P availability of PYC . Treatments applied to the soil in the greenhouse and field studies consisted of various levels of P as Ca(H₂PO₄)₂.H₂O, PL and PYC from 15:1, 20:1, and 25:1 C:N ratio substrates. Each P source increased dry weight of corn plants grown in the greenhouse by alleviation of P deficiency. Phosphorus uptake from PYC and PL application was either equal to or higher than P uptake from an equal level of P application as Ca(H₂PO₄)₂.H₂O. Application of 87.2 kg of P per ha increased corn grain yields in a field experiment on Vance sandy loam from 6340 kg per ha on the control to a range of 10,170 to 11,350 kg ha for PYC digested from the three C:N ratio substrates. The yields on PYC treatments were attributed to a combination of factors including slow mineralization of P with less fixation during the growing season. The low P fixing capacity results from the blockage of H₂PO₄⁻ sorption by competition of negative charge from organic material and from the displacement of H₂PO₄⁻ in soil solution by OH⁻ from application of the alkaline composts. It would be desirable from the standpoint of more PL utilization to prepare composts from low substrate ratio substrates. Hence, in this research composts were prepared from 15:1, 20:1, and 25:1 C:N substrates, which consisted of PL and YW. The composting process was complete after only four months for the PYC from the 20:1 and 25:1 C:N ratio substrates. Yard waste compost without PL may require somewhere between two to three years for complete composting as opposed to four months with PL addition. The composting was incomplete in four months (presence of undigested leaves and NH₃) for the PYC from the 15:1 C:N ratio substrate. The latter compost resembled poultry manure rather than a high quality compost after the 4-month composting period.
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    Engineering properties of selected soils in the Virginia Piedmont
    Parker, Jack C.; Amos, Dan F.; Baker, James C. (Virginia Agricultural Experiment Station, 1983-10)
    The Piedmont Province i Virginia, running in a north-south direction, is approximately 50 miles wide along the Maryland border I ard broadens to the south until it encompasses approximately 150 miles along the North Carolina border. It cor prises at least one-third of the land area of the stat , with approximately 60% occupied by woodland and 40% by agriculture, primarily beef or dairy enterprises. Located in the Piedmont j:e the cities of Leesburg, Fairfax, Manassas, Warrenton, Culpeper, Charlottesville, Lynchburg , Bedford, Farmville, Martinsville, Danville and South Boston. I an McHargue, in his book Design With Nature, studied the Potomac River watershed and concluded that "the Piedmont is primaril suitable for urbanization with attendant agriculture and undifferentiated recreation" (McHargue 1969). Because of the development potential of the Piedmont and the intense pressures for future urbanization west of Washington, D.C., in the counties of Fairfax, Prince William and Loudoun; around Richmond in the counties of Hanover, Hen ico, Goochland, Powhatan, Amelia and Chesterfield; an in Albemarle, Amherst, Bedford, Campbell, Franklin, Henry and Pittsylvania counties, the need to intensively study the most widely distributed and potentially important Piedmont soils became apparent....
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    Factors affecting loblolly pine growth following site preparation
    Needham, Ted Daniel (Virginia Polytechnic Institute and State University, 1986)
    Site preparation is a required silvicultural practice for establishing loblolly pine plantations in the Piedmont physiographic region of the southeastern U.S.; however, relatively little is known about its effect on soil and site factors that influence growth and yield. In this study, the effect of seven different site preparation prescriptions on competing vegetation, tree nutrition, and the spatial distribution of planted seedlings was examined. Three treatments had a soil tillage component and differed with respect to the number of operations employed in removing residual trees and logging slash prior to discing. One treatment involved roller chopping and broadcast burning, one an application of the herbicide glyphosate followed by a broadcast-burn, one involved shearing all raking fogging-debris into windows, and one was no site preparation prior to planting. All treatments were applied to 12 sites in the South Carolina and Georgia Piedmont. After four years in the field, 756 trees within the site preparation treatment areas were randomly selected for analysis of foliar nutrients, soil nutrients, and competing vegetation. Herbaceous, woody shrub, and hardwood competition levels were not significantly different among site preparation treatment areas after four years. However, hardwood competition levels had increased at a faster rate during the last two growing seasons on chopped and disced areas than on the other areas. Hardwood competition became the predominant factor limiting pine basal diameter when 83% of the total basal area was in hardwoods or hardwood basal area levels exceeded 3.5 m²ha⁻¹. Potassium was identified as the most limiting nutrient 38% of the time, compared to 28% for phosphorus, 14 % for nitrogen, 7% for calcium, aiid 13% for magnesium. A significant linear relationship between soil and foliar nutrients confirmed these results. No treatment effect on nutrient deficiencies was evident. Foliar nutrient critical levels were derived using the Diagnosis and Recommendation Integrated System (DRIS) and were the same as those reported in the literature for nitrogen, phosphorous, and magnesium while potassium and calcium critical levels were determined to be twice as high as those reported (0.52% and 0.19%, respectively). The spatial distribution of seedlings at planting and after 2 years was determined. Spatial patterns varied from uniform to random as the degree of logging slash removal decreased. After two years, the spatial distribution shifted toward random and clustered. The degree of change was similar in all but the herbicide burn and untreated areas, which exhibited the greatest change and whose mortality tended to be clustered.
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    Field efficacy and availability, movement, and persistence of ICIA-0051 herbicide in soils
    Wilson, John Samuel (Virginia Polytechnic Institute and State University, 1989)
    Fields studies conducted in 1987 and 1988 determined the weed control efficacy of ICIA-0051 and SC-0774 in conventional and no-till systems of corn (Zea mays L.) culture. Results of the preemergence and postemergence applications of ICIA-0051, across all treatments after 8 weeks, showed 85% control or better of triazine-resistant smooth pigweed (Amaranthus hybridus L.), while fall panicum (Panicum dichotomiflorum Michx.) control ranged from 43 to 87%. Giant ragweed (Ambrosia trifida L.) control ranged from 30 to 95%, while control of ivyleaf morningglory (Ipomoea hederacea (L.) Jacq.) was below 75% in the preemergence treatments and ranged from 89 to 99% in the postemergence treatments. In general, the addition of atrazine to the pre- and postemergence treatments of ICIA-0051 improved weed control. SC-0774 treatments gave 85% or better control of fall panicum, but inadequate broadleaf weed control (75% or worse). Soil mobility studies using soil thin-layer chromatography and soil leaching columns indicated that the movement of ICIA-0051 was highly negatively correlated with the organic/humic matter fraction. Although the mobility patterns were similar, ICIA-0051 was more mobile than SC-0774, which was more mobile than atrazine. A comparison of ICIA-0051 across soils indicated that the order of mobility was Appling loamy sand (Rf = 6.4) > Davidson clay (Rf = 5.6) > Bojac sandy loam (Rf = 5.0) = Frederick silt loam (Rf = 4.9) > Hyde silty clay loam (Rf = 1.1). Other soil properties such as the clay content and pH were not strongly correlated with ICIA-0051 movement. Results of the adsorption/desorption studies indicated that the organic/humic matter fraction was primarily responsible for the binding and retention of ICIA-0051 across the five soils investigated. Based on the K constants derived from the Freundlich equation, the order of adsorption was Hyde > Frederick > Davidson = Bojac > Appling. The desorption results indicated that ICIA-005l was not tightly bound to the soil particles, with losses between 20 and 50% of the amount adsorbed after two desorptions. Results of the greenhouse persistence study, using mustard (Brassica kaber L.) as a bioassay species, indicated that ICIA-0051 was more biologically available than atrazine. Similar to the adsorption and leaching results, the persistence of ICIA-0051 was highly positively correlated with the soils’ organic matter. Regardless of the rate used, crop injury decreased over time, although the highest rate (1 ppm of ICIA-0051) showed significant crop injury even after 6 months in several soils in the greenhouse studies.
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    Impact of Conservation Tillage on Soil Erosion and the Agronomic Performance of Flue-Cured Tobacco
    Jones, Bruce (Virginia Tech, 1998-12-08)
    Conservation tillage tobacco production has gained little producer acceptance since introduction in the late 1960's. Yield reductions, tobacco quality issues, unacceptable weed control, and inadequate planting equipment limited practice adoption and substantiated the need for continued research. The recent developments of a Subsurface Tiller-TransplanterTM and the herbicide SpartanTM renewed producer interest in conservation tillage and led to an investigation with both flue-cured and Virginia dark-fired tobacco. Flue-cured tobacco was transplanted into rye mulch on bedded rows and subsequently cultivated at various timings. Conservation tillage significantly reduced soil erosion approximately 92 percent and tobacco yield approximately 23 percent when row cultivation was not applied. Row cultivation significantly increased tobacco yield without increasing soil erosion. The yield of conservation tillage tobacco receiving a minimum of two cultivations was similar to conventional tobacco. The second study evaluated wheat, rye, crimson clover, and mixtures of crimson clover with either wheat or rye as cover crop mulches for conservation tillage production of Virginia dark-fired tobacco. Conservation tillage, regardless of cover crop, reduced dark-fired tobacco yields approximately 779 and 488 pounds per acre in 1996 and 1997, respectively. The removal of cover crop residue for hay did not lower tobacco yield compared to leaving residue on the soil surface. Row cultivation increased conservation tillage tobacco yield approximately 247 pounds in 1997 regardless of cover crop. The nitrogen contribution of crimson clover was minimal in both years of the study and did not affect tobacco performance.
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    The influence of particle size on the chemistry of mica clays
    Gassman, Paul Lawrence (Virginia Tech, 1990-02-15)
    In order to assess the importance of particle size on elemental composition, structure, morphology, and charge characteristics of 2:1 micas, mechanically produced clay separates were analyzed by; electron probe microanalysis (EPMA), transmission electron microscopy (TEM), thermogravimetry, specific surface area analysis, and ion exchange. Books of biotite and muscovite were reduced to clay size « 2.0 μm) particles by mechanical comminution, then further fractionated into coarse (0.2-2.0 μm), medium (0.08-0.2 μm), and fine (< 0.08 μm) clay sizes. Composition of the clay size micas was particle size dependent, compositional changes being smaller for the medium and coarse clays. Grinding produced significant losses of interlayer K, decreased crystallinity, but increased water content as particle size decreased. The medium and coarse clays maintained coherent basal diffractions, whereas, significant peak broadening of x-ray diffraction maxima was observed for the fine clays. Diffracted peak broadening was due to the reduced crystallite size and the semirandom orientation of lath shaped particles. Specific surface area, adsorbed water. and structurally coordinated water increased as particle size decreased. Specific surface areas were determined by adsorption of molecular nitrogen, at liquid nitrogen temperatures. The increased water contents were measured by thermogravimetric analysis. An increase in CEC of the muscovite clays was detected with decreasing particle size, increasing solution pH, and increasing ionic strength. Assignment of specific exchange capacities for the three clays was confounded by AI hydrolysis and depressed solution pH.
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    An investigation of soils within the Tatum and Elioak mapping units in the Virginia Piedmont
    Wilson, M. A.; Zelazny, Lucian W.; Baker, James C. (Virginia Agricultural Experiment Station, 1983-03)
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    Leaching and denitrification losses of nitrogen from corn fields as influenced by conventional- and no-till practices in soils of the Chesapeake Bay area
    Menelik, G. (Virginia Tech, 1990)
    Research was conducted in soils of the Chesapeake Bay area primarily to determine the combined effects of tillage practice and N fertilizer application rates on N leaching and denitrification losses from corn fields. Three well known models - the NTRM, CERES- Maize, and VT-MAIZE - were also tested to determine their predictive ability of N distribution in soil and crop, the various components of the N cycle, and corn yields. To accomplish the above objectives, two field sites were located (in 1986) for a 3 year study on agronomically important and representative soils that are used for corn production in the Chesapeake Bay drainage basin. The main plot treatment was tillage and consisted of no-till and conventional-till. The subplot treatments were N application rates which consisted of 6 levels with 4 inorganic and 2 organic (sewage sludge) N fertilizers. Denitrification experiments were also conducted on the Groseclose silt loam soil to estimate and compare N loss through denitrification from both till and no-till practices. C₂H₂ was used to inhibit N₂ production and N₂O was collected in closed chambers located on the soil surface. Tensiometers and neutron moisture meter access tubes were also installed to monitor soil moisture and energy levels. Nitrogen leaching losses were determined by applying the principle of N mass balance. Denitrification N loss during the corn growing season was less than 2% of the applied N fertilizer. The N losses from the two tillage systems were not significant at p > 0.10. If Fick’s law is to be applied for predicting N loss from the soil subsequent to C₂H₂ application, sampling must occur after a minimum preset critical time. In the Groseclose soil, there was an increase in both total yield and total N uptake when sewage sludge was applied compared to the split and preplant inorganic fertilizers applied at the same rate. There was no difference in yield or N uptake due to applying N as either preplant or a split application. Where no-till management was used, there was an increase in both yield and N uptake as compared with conventional tillage. In the Suffolk soil, tillage management did not influence yield or N uptake where time and source of N application were studied. The relationship between yield and N application rates for both soil types could be described with quadratic equations. The total N recovery could also be described with quadratic equations. However, these relationships do not hold every year for every season or tillage management practice. The no-till plots retained higher moisture content than conventional tillage plots in the upper 0-100 cm depth. Below 100 cm depth, however, no-till retained less than conventional till. The gain and loss of N in soil was dependent on the tillage type and seasons of the year. During the growing season, generally the conventional tillage gained more N than the no-till. During winter, however, the N losses due to leaching were proportional to the amount of N retained at the end of the growing season. Thus, conventional tillage lost more N by leaching during the winter months. Mineralization of N was higher in conventional till, while denitrification was higher in no-till. Split application has shown less N loss due to leaching than the preplant. Mineralization, denitrification, and leaching took place from both the upper and lower zones of the soil profile. The model performances varied from year to year and from one tillage practice to another. Since they were generally written for average (normal) soil and climatic conditions, they did not make satisfactory predictions under the severe moisture conditions experienced during this study. Thus, they require a great deal of readjustment. Considering all aspects, however, the NTRM is the best model. The unmodified VT-MAIZE is the next best.
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    Management of Alum-Treated Poultry Litter
    Warren, Jason George (Virginia Tech, 2005-12-13)
    Previous research has shown that treatment of poultry litter with alum is an effective management strategy to reduce phosphorus (P) solubility in litter thereby reducing potential P losses to surface runoff after surface applications. However, limited data are available evaluating alum-treated poultry litter (ATPL) environmental impact in cultivated systems and how its application will affect crop production. In addition little is known as to how its application affects various P fractions or exchangeable Aluminum (Al) content in treated soils. Two, 3-yr field trials with corn (Zea mays L.) were used to show that, when applied at rates based on current litter management strategies, ATPL resulted in yields similar to those achieved through applications of non-treated poultry litter (NPL). These trials also showed that ATPL applications resulted in lower soil P status and decreased P losses in surface water runoff compared to application of NPL. A 4-yr field trial with fescue (Festuca arudinacea) also showed no significant differences in productivity when comparing ATPL and NPL. This trial was utilized to evaluate the distribution of P in soils receiving ATPL. Soil analysis data showed that ATPL applications result in decreased water-extractable P (H2O-P) and that this decrease was associated with an elevation in NaOH extractable organic soil P. A laboratory incubation was utilized to evaluate the short and long-term impact of ATPL application on soil pH, exchangeable soil Al and H2O-P. Data from this incubation confirmed that the relationship between soil pH and exchangeable Al is not adversely affected by ATPL applications. Also, variations in the H2O-P content of soils treated with two different ATPL sources could not be associated with differences in Al:P ratio or soluble P content of the two litters, providing evidence that additional characteristics also control P availability after incorporation in soil.
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    Measurement of hydrolysis, polymerization and complexation in dilute aluminum solutions
    White, George Norman (Virginia Polytechnic Institute and State University, 1987)
    The nature of chemical reactions taking place during the titration of dilute Al solutions in the presence of either chloride or sulfate were examined by refining the apparent Al hydrolysis products assuming the presence of solution species with n (OH/Al mole ratio) equal to 1, 2, 2.5, 3 and 4. The second and third hydrolysis products for Al were refined by comparison of calculated titration patterns to those observed for 10⁻³, 10⁻⁴ and 10⁻⁵ M Al in 1 M, 0.1 M and 0.01 M KCl. A large degree of polynuclear character of Al solutions was found even at Al concentrations as low as 10⁻⁵ M. The n value and size of the polynuclear complexes are affected by Al concentration. The concentration constant, pQ₁₃ is found to be at least 17.4-17.7. It is concluded that the mononuclear Al(OH)₂ species is never significant. Use of statistical analysis of the data and graphical methods did not result in consistent data for polymer size determinations. The lower pQ values for mononuclear Al hydrolysis are explained by the structural instability of the mononuclear complexes. The bond strengths required for the bonds in the second and third hydrolysis complexes are often larger than those allowed for octahedral coordination. For that reason, the pQ values would be lower than calculated by extrapolation between the stable first and fourth hydrolysis constants. A new polynuclear complexation mechanism for Al is proposed to account for the high concentration of high n value polynuclear species in the titration refinements. The proposed linear l double chain structure has a structure consistent with boehmite and diaspore. This structure differs from the linear single chain and ring based polynuclear structures by the presence of rows of three coordinated oxygens in the bond central chain and rows of two and one coordinated oxygens along the plane edges. A rearrangement of internal charge in this structure is proposed in which part of the charge is removed from the three coordinated oxygens to result in an uncharged hydroxyl with the charge shifted to the one coordinated site neutralizing the hydroxyl. This results in a general formula for the polynuclear structure of (Al(OH)₃)x(Al(OH)₂)₂²⁺. This structure results in a higher n value for a lower number of Al than does the other polynuclear complexation schemes and therefore explains the presence of high n value polymers in unaged Al solutions which would have required polymers of greater than a hundred Al cations. The observed presence of a second Al plateau on titration patterns with Al concentrations greater than 5 x10⁻⁵ M could not be the result of the onset of precipitation as earlier proposed. It is proposed that at a pH in the 6 to 7 range, a change of some of the one coordinated sites on the edge of the larger polynuclear and precipitant structures from water to hydroxyls results in a change in net edge charge from net positive to net negative which causes an increased rate of crystal growth due to the unlike charge between the edges and the smaller polynuclear and mononuclear complexes. The refinement of Al titration data in K₂SO₄, provide pQ values one to three pQ units lower than those obtained from equivalent KCl solutions. A catalytic mechanism is proposed in which Al polymerization is facilitated by the formation of mononuclear Al hydroxy sulfate complexes which combine together to form nonsulfate containing polynuclear complexes. The increased hydrolyzed concentration and lower ionic charge resulting from these complexes would increase the rate of polymerization in these systems. Evidence for the presence of mononuclear hydroxy sulfate complexes comes from the better fit for titration patterns in sulfate systems which would not have been observed for increased polymerization alone.
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    Nutrient Management Planning on Virginia Livestock Farms: Impacts and Opportunities for Improvement
    VanDyke, Laura Snively (Virginia Tech, 1997-01-31)
    This study provides an environmental and economic analysis of the ability to reduce potential nitrogen loadings to water bodies through the implementation of nutrient management plans on livestock farms. Study results indicate that nutrient management plans do result in significant reductions while maintaining or increasing farm income. Nutrient management plans on the four case farms reduced mean nitrogen losses by 23 to 45 percent per acre while increasing net farm income from $395 to $7,249. While reducing excess nitrogen applications with the implementation of nutrient management plans achieved significant reductions in potential nitrogen losses, further reductions may be achieved through farm level planning. After achieving initial reductions through the elimination of excessive nutrient applications, variation in application rates of organic and inorganic fertilizers across soils may become important in achieving further reductions in nitrogen loss. Study results suggest that it may be beneficial to apply higher rates of manure on soils and slopes less susceptible to nitrogen losses in order to reduce applications elsewhere. Increased nutrient losses on such fields may be more than offset by reductions on soils more susceptible to nutrient losses. Linear programming results for the Shenandoah Valley Dairy show that nitrogen losses could be reduced up to 44 percent below pre-plan losses with no impact on farm net economic returns. However, if nitrogen loss restrictions were instituted beyond this level, the impact on farm income increases significantly. After-plan nitrogen losses can reduced up to 52 percent, but farm returns decrease by 56 percent.