VTechWorks Repository :: Browsing by Author "McKenna, James R."

Browsing by Author "McKenna, James R."

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Agroforestry opportunities and constraints in the Água de Gato Watershed, Santiago, Cape Verde Islands
Delgado, Orlando Jesus (Virginia Tech, 1996-08-23)
The objectives of this study were to determine the opportunities, constraints, and willingness of the inhabitants and non-resident landowners to adopt a new land-use system in the Agua de Gato Watershed, to determine the degree of agroforestry technical support available to farmers in the watershed, and to determine suitable agroforestry systems which can be adapted to the watershed according to its biological and physical conditions. A random group of farmers of the Agua de Gato Watershed and a group of technicians working on the island of Santiago were interviewed in order to get individual and general information about the farms the and practice of agroforestry in the watershed. Only 56% of the technicians knew or had some knowledge about agroforestry, and the farmers think that they do not have enough technical support for better development of agriculture in the watershed. Although most of the farmers had a small piece of land, averaging 1.1 ha, most of them, 92%, were willing to adopt an agroforestry system as a new land use system for their farms.
Combining ability, protein, heterosis, and prediction of F₁ performance with RFLPs in a diallel of maize
Ball, Dale Warren (Virginia Tech, 1994-07-06)
Improving protein quality and identifying superior inbreds and hybrids are significant challenges in commercial maize breeding programs. These two problems were addressed in separate studies on inbreds and hybrids from a complete diallel cross of 12 elite proprietary inbred lines of maize evaluated in field trials in two locations for two years. One of the inbreds (WI) was a novel source of high quality protein obtained from Wilson Seeds, Inc. in Harlan, Iowa. In the first study, diallel analyses were used to study combining ability and types of gene action important in the inheritance of protein content, grain yield, grain moisture at harvest, time to silk, kernel hardness, and density. General combining ability (GCA) and specific combining ability (SCA) effects were highly significant for all traits indicating presence of both additive and non-additive effects, respectively. Reciprocal effects (REe), often assumed to be absent in maize diallel studies, were significant for grain yield and protein concentration, suggesting that choice of female parent may be important for these traits. Ratios expressing the relative importance of GCA and SCA indicated that protein concentration is controlled primarily by additive gene action. In the second study, restriction fragment length polymorphism (RFLP) data were obtained for the 12 inbreds using 42 genomic clones each with four restriction enzymes. Modified Roger's distances were calculated and used in cluster analyses for heterotic grouping of the inbreds. Two measures of level of heterozygosity and hybrid value were evaluated as means of predicting Fl performance of hybrids in the complete diallel set of hybrids and in groups of hybrids representing crosses between and within heterotic groups. Results from this study confirm those of previous investigations with respect to prediction of hybrid performance when comparable groupings of crosses between related and unrelated lines were evaluated. This study further indicates that RFLPs may also be useful for prediction of hybrid performance in situations typical of early generations of many maize breeding programs where recombinant inbreds are testcrossed to a common tester inbred.
Compatibility, Yield, and Quality of Warm-Season Grass-Legume Mixtures
El Hadj, Meriem (Virginia Tech, 2000-06-09)
The lack of consistent summer pasture supply is a major limitation to livestock production in the mid-Atlantic region. Perennial warm-season grasses might provide a solution if managed for high quality. Experiments were conducted on separate well-established stands of Caucasian bluestem and 'Cave-in-Rock' switchgrass at the Kentland Farm near Blacksburg, VA. Stages of grass maturity at harvest simulating pasture and hay systems were tested. Six interseeded legume species and two grass monoculture checks, one with 56 kg N/ha applied in spring and after each harvest, the other with no N, were imposed as sub-plots. Legume species included alfalfa, red clover, sericea lespedeza, annual lespedeza, Illinois bundleflower, and purple prairieclover. Inter-seeded legumes contributed a significant amount to yield and quality of perennial warm-season grasses in the legume-establishment year. In the year after establishment, grass mixtures with alfalfa, red clover, and, for switchgrass, sericea lespedeza yielded as much forage as N-fertilized grasses. Alfalfa and red clover altered the distribution of yield of the grasses, and may not be as compatible with perennial warm-season grasses as sericea lespedeza in the long-term. Interseeded legumes improved quality considerably in the second year.
Defining a Global Learning Environment in Higher Education: A Case for the Global Seminar Project
Savelyeva, Tamara (Virginia Tech, 2008-09-11)
In this study I defined the global learning environment (GLE) as it appeared in the Global Seminar Project (GSP) to address the issues of change in higher education under the pressure of globalization. The combination of constructivist theory and a Biggs' (2003) deep learning concept provided a framework for answering the following research questions: (a)what project components make the course global? and (b)in what ways does the Global Seminar contribute to deep learning? For the purposes of this study, I used three forms of data collection, including in-depth, open-ended interviews of 20 GSP's instructors; 11 direct observations of the GSP classroom; and analysis of GSP's written documents and artifacts. I used the open-coding feature of ATLAS.ti software to analyze the interview data and identify the descriptive themes that emerged from the observations and documents. The interview analyses revealed that the GSP's global learning environment included five areas: (a) course structure and academic leadership/management; (b) stakeholder involvement; (c) institutional support; (d) course conducive content; and (e) teaching and learning practices. Within these five major areas I indicated four "global" categories of the learning environment established in the course: innovative, international, interactive, supported by the culture of mutual learning. Evidence of deep learning included observed development of students' generic metacompetencies, identified components of instructors' teaching quality, and recognized value of the relationships among course participants. The research findings brought about two co-dependent understandings of the GLE as a conceptual phenomenon and a practical model. As a conceptual phenomenon, the GLE can be defined as a specific property of an educational structure that occurs when teachers and students are engaged in innovative experiences with the purpose of acquiring understanding of complex global-scale issues by means of cross-cultural interactions and on the basis of mutual learning. Applied to an educational practice, this understanding of the GLE forms a constructive and participatory model that provides possibilities for transforming higher education practices: shifting from mass-production knowledge to genuine quality education based on the values of teachers. These conclusive definitions open a dialogue regarding how the GLE can initiate meaningful changes in educational theory and practices.
Developing methods of strip cropping cucumbers with rye/vetch
Ogutu, Maurice Okendo (Virginia Tech, 2000-11-20)
The purpose of this research carried out in 1998 and 1999 was to develop methods for strip cropping of cucumbers with rye/vetch and black plastic mulch. Effects of planting methods, weed control measures, and cover crop management techniques on pest and beneficial insects, petiole sap nitrate-nitrogen, soil moisture, yields and economic viability were assessed. Four treatments, namely cucumber direct seeded in black plastic mulch on tilled bare ground (conventional); cucumber direct seeded in black plastic mulch laid over incorporated rye/vetch residue; cucumber direct seeded into no-till rolled rye/vetch; and seedlings transplanted into no- till rolled rye/vetch, were evaluated in a randomized complete block design. Weeds were controlled in half the plot by critical manual weeding and pre-emergence herbicides applied in the other half in all treatments except the conventional system. Three-week interval staggered plantings of buckwheat to provide flowers for adult beneficial insects were also evaluated. Results obtained indicate that rye/vetch habitat is more attractive to beneficial insects than cucumber beetles before rolling or flail mowing. There were higher densities of adult Diptera (an indicator for Tachinid parasitoids) in both years and of Pennsylvania leatherwings in 1999 in plots with rye/vetch than in plots with rye only before planting. Preferential attraction to adult Diptera was not found after planting with no differences in cumulative densities between no-till and black plastic mulch plots after rolling or flail mowing. However, adult Diptera densities were positively correlated with cucumber yield, higher densities of cucumber beetles occurred in black plastic mulch than in no-till plots in both years, and bacterial wilt, transmitted by cucumber beetles, was reduced in no-till in 1999. Similarly, rye/vetch habitat plots had a higher diversity of Carabidae species (in both habitat areas and crop rows) before rolling or flail mowing, and higher densities of Carabidae (in habitat areas), Staphylinidae (in both habitat areas and crop rows) and spiders (in crop rows) after rolling or flail mowing. Black plastic mulch plots with flail mowed, incorporated rye/vetch residues had higher petiole sap nitrate-nitrogen and higher early season cucumber plant dry weights than in conventional plots; later in the season, the highest petiole sap nitrate-nitrogen occurred in no-till plots. No-till had higher marketable cucumber yield than plastic systems. The profitability of these production systems depended more on differences in marketable yield than on cost differences. The plastic with incorporated rye/vetch and no-till transplant systems were more profitable during early harvests in late July, while no- till direct seeded and transplant systems were more profitable from early August onwards. The three-week interval staggered planting of buckwheat led to conservation of beneficial insects, and the second and third seeded buckwheat flowering periods coincided with the period vetch had lost flowers.
An economic analysis of nitrogen fertilization regimes in Virginia
Maiga, Alpha S. (Virginia Tech, 1992-09-15)
The loss of nitrogen from agricultural land to ground and surface waters is currently a major concern in the Commonwealth of Virginia. Farmers use nutrients on plants to maximize profit from the selling of a crop. For them losses of nutrients through inappropriate nutrient application are undesirable. Thus more effective nutrient management is beneficial for both the farmers and the remainder of society. Achieving environmental quality goals while taking into account farmers' income risk is essential when making fertilization recommendations. This study on Richmond county, uses the EPIC model and stochastic dominance analysis to compare four different fertilization regimes at the field and farm level; and then uses a sensitivity analysis to examine how the ranking of different regimes are affected by changes in crop prices. Results suggest that regime 4 which is the EPIC automatic fertilization regime has a better performance than the other regimes. However potential costs not accounted by EPIC involved at the farm level when using regime 4 may negatively affect its adoption by farmers. Thus further studies need to be done to understand and assess the performance of regime 4. The results do not show any significant difference between farm and soil type levels of analysis. The sensitivity analysis mainly affects the less risk averse decision makers, and change only the ranking of the three fertilizer regimes specified by the researcher as opposed to the automatic fertilizer option of EPIC.
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.
The Factors Affecting Elementary School Teachers' Integration of School Gardening into the Curriculum
DeMarco, Laurie W. (Virginia Tech, 1997-04-21)
The purpose of this research was to identify the logistical, conceptual, educational, and attitudinal factors that affect elementary school teachers’ implementation of school gardening in the curriculum. This research also sought to qualitatively describe the current application of school gardening by the study population in the elementary school curriculum, and to identify avenues in which the horticultural community can assist teachers in implementing the use of this teaching strategy. The target population consisted of elementary school teachers who taught at schools that had received a Youth Gardening Grant from the National Gardening Association in either the 1994/95 or 1995/96 academic years. Data were collected using a School Gardening Survey which was sent to an accessible population of 315 elementary schools. From this mailing, 236 usable responses were received for analysis. The results of the survey were confirmed, and expanded upon, by personal interviews conducted with 28 teachers from the test population who used school gardening in their curriculum and taught in the Commonwealth of Virginia. Survey and interview responses provided data for statistical analysis using the computer statistic package, Statistical Analysis System (SAS). Chi-square correlations did not provide significant relationships between factors; however, frequencies, averages and mean and mode information provided insight into the use of school gardening and the needs of teachers who are using this teaching strategy. Survey data indicated that the most important factors that need to be present for the successful use of school gardening were logistical factors. The most essential factors were a person, or persons, who take on the responsibility for the gardening program, the availability of a site to grow plants, and adequate funding for gardening materials. In addition, the availability of gardening equipment and the support of the principal were stated to be very important to school gardening success. Interview data indicated that the most crucial factors that need to be present for the successful use of school gardening were educational factors. Student ownership of the gardens and the integration of school gardening into the curriculum were seen as more important to school gardening success than the logistical features of school gardening. There was survey and interview consensus, however, that the lack of preparation time for school gardening activities and the lack of instructional time for learning using school gardening were factors that influence the use of this teaching strategy. There was also agreement that the logistical factors of a growing site, a water source, the availability of gardening equipment, adequate funding, and a person who is responsible for school gardening were important to the successful use of school gardening. Essentially all of the interviewed and surveyed teachers (99%) use school gardening as an interdisciplinary teaching method. It is the interdisciplinary nature of gardening and growing plants that allows school gardening to be used successfully within the elementary school curriculum. Study results also indicated that school gardening is used to teach students in all grade levels found in an elementary school including students in prekindergarten, special education, and 3English as a Second Language2 classes. School gardening is often used to benefit students beyond standard academic achievement. Teachers use school gardening for such goals as social development, therapy, recreation, environmental awareness, community relationships, exploring diversity, and the arts. School gardening is also seen as a teaching strategy that can occur both indoors and outdoors. Teachers are not limiting their concept of gardening to an activity that must occur in the out-of-doors. Teachers indicated that they depend primarily on their own knowledge of gardening when gardening with their students. They also rely more on their gardening knowledge than on their knowledge of science when using school gardening within the curriculum. However, these same teachers expressed a need for further education and information on the integration of gardening into the curriculum, and the horticultural aspects of gardening that can be implemented within the educational, time, facility, funding, and legal limits placed on a school situation. Teachers also requested that this education be provided as in-service training, Master Gardener training, or graduate and/or continuing education classes provided through the local institution of higher education. The survey and interview respondents indicated that school gardening is a very effective, interdisciplinary teaching method. These teachers find that use of school gardening assists students in learning and understanding new ideas, and that student learning improves when using school gardening in the curriculum. In addition, interviewed teachers indicated that students obtain a more positive environmental ethic when gardening is used in the curriculum. Elementary school teachers may use school gardening to improve student academic and social achievement, to provide a hands-on learning experience that reaches across the curriculum, to furnish a forum that provides opportunities to learn such positive social qualities as nurturing life and responsibility, and to encourage students to expand their appreciation for the living world around them. The interdisciplinary nature of school gardening shows promise as a teaching strategy that can be used to enhance student learning, and to expose students to the expanse of learning available through the process of growing plants.
Financial Performance of Pasture-Based Dairies: A Virginia Case Study
Groover, Gordon E. (Virginia Tech, 2001-04-02)
Virginia dairy producers are considering intensive grazing as a profitable and ecologically viable alternative to confinement dairy production. The objective of this study is to compare financial performance for pasture-based dairy farms relative to similar resourced-based confinement farms. Comparisons are based on the recommended financial and profitability measures of performance provided by the Farm Financial Standards Council. Primary and secondary data plus simulation of daily pasture supply and animal demands are used to develop 100 and 200-cow farms with a land base representative of the Ridge and Valley regions of Virginia. Representative farms were developed to explore financial performance based on the intensity of pasture use, from total confinement to seasonal farms using intensive grazing (in which pasture, hay, and energy supplements are the only sources of nutrients for all dairy animals on the farm). Results of the analysis demonstrate that pasture-based seasonal production is more profitable and has a higher level of repayment capacity and financial efficiency than all other production systems in this study. Greater financial performance by the seasonal farms is obtained even though such farms obtain lower average annual milk prices and 10 percent less milk sold per cow than the similar confinement farms. Pasture-based farms that feed a partial total mixed ration during the summer (25 percent of ration dry matter and 45 percent of ration dry matter from pasture) have fewer financial advantages than the seasonal farms. However, their performance exceeds that of the confinement farms and intensive pasture-based farms milking year round. The intensive pasture-based farms milking year round are the poorest financial performers. Additional conclusions for this study are: 1) the 100-cow farms exhibit insufficient financial performance to provide for family living, debt service (at 40 percent debt to equity ratio), and a cushion for events such as droughts or declines in milk prices; and 2) financial performance of the 200-cow dairies is better, yet the added income from a member of the farm having off-farm income will provide a cushion against unforeseen production and financial risks. Follow up research should address the interface of three issues; stocking rates, farm profitability, and environmental compliance.
Flue-cured tobacco: alternative management systems
Clarke, C. Taylor Jr. (Virginia Tech, 1996-05-05)
The United States share of the exported flue-cured tobacco market has decreased over the last decade as other countries have increased production of improved quality tobacco. Such tobacco is available at a substantially lower price than U. S. tobacco and thus desirable for the manufacture of less expensive discount cigarettes. Although world consumption of American style cigarettes is increasing, demand is not sufficient to maintain current production levels of premium quality U. S. flue-cured tobacco. Production systems that increase yields of suitable quality tobacco for discount cigarette manufacture without increasing production costs would allow tobacco to be offered competitively on the world market while maintaining current income. A study of ten management systems was conducted evaluating the influence of plant spacing, topping height, and harvest method on yield and quality of flue-cured tobacco. Leaf populations of 538,000/ha harvested once-over resulted in a 6.5%, 11.0%, 6.0%, and 13.5% increase in yield, value, price, and grade index, respectively, compared to the standard treatment. An expert panel showed no preference among systems and judged all systems acceptable in quality. A study conducted as a randomized complete block in a split plot arrangement evaluated the influence of row spacing and plant spacing on the yield and quality of flue-cured tobacco harvested once-over. Yield, value, and grade index increased while price per kg was unchanged as plant population increased. Flue-cured tobacco harvested in a single harvest produced cured leaf of acceptable quality; however, increased leaf populations are required to maintain acceptable yields.
Forage Production and Nutritive Value in a Temperate Appalachian Silvopasture
Buergler, Alicia Lenore (Virginia Tech, 2004-04-28)
Integrating trees into pasture may be an effective management tool to improve water, nutrient, and light allocation and increase total system productivity in Appalachia. We tested this hypothesis in a silvopasture near Blacksburg, VA. In 1995, black walnut and honey locust trees were planted within plots (r=3) of predominantly tall fescue pasture. Across a 12% slope, trees were planted to create treatments of low, medium, and high tree densities at shoulder, mid, and toe slope positions within plots of honey locust and black walnut. Sampling sites (n=54) under tree density and slope position combinations were harvested May to October at 35-d intervals in 2002 and 2003 for determination of yield and nutritive value characteristics. Soil surface temperature, forage canopy temperature, soil moisture, and photosynthetically active radiation were measured to determine forage responses to field treatments as functions of resource allocation. Tree density had the greatest effect on forage production and nutritive value. Across both years, yields were 16% greater (P=0.0006) at medium density (6130 kg/ha) compared to forage mass at low (5280 kg/ha)) and high density (4970 kg/ha, SE=130). Increasing tree density did not affect (P>0.2) ADF, CP, P, K, and Mg levels, but reduced (P<0.001) NDF and TNC, and increased (P<0.0001) ADL and Ca. Elevated soil surface and forage canopy temperatures limited forage production and nutritive value at low density, while low light levels were the limiting factor at high density. Moderating forage microclimate with appropriately spaced trees is an effective way to improve forage production in temperate pastures.
Hair Sheep Production in Temperate, Deciduous Appalachian Silvopastures
Fannon-Osborne, Amy Gail (Virginia Tech, 2012-07-02)
Silvopastoral management has potential to diversify and increase the output from livestock production systems. Silvopasture production offers solutions to many management issues associated with grazing systems in the Appalachian region. Several tree species have been proposed for silvopastures in humid temperate regions, but little data comparing animal performance from systems with different deciduous tree species are available. Forage and animal performance was compared from open systems (i.e., no trees) with that from silvopastures containing 13-yr-old honeylocust (Gleditsia triacanthos) or black walnut (Juglans nigra) trees. Cool-season grass-legume pastures were rotationally stocked with hair sheep crosses from mid-June through September. The objective of this project was to determine carcass characteristics and meat quality of hair sheep crosses grazing honey locust or black walnut silvopastures in comparison with traditional pasture systems. Forage production varied by year with black walnut having lower production, especially in the 2009 season with black walnut producing less forage compared to open pastures and honeylocust silvopastures (P=0.0008). Only small differences in forage nutritive value were observed. Total gains and average daily gains (ADG) did not differ by treatment in 2008, but during the 2009 season black walnut silvopastures produced half the total gains (P=0.0427) and ADG (P=0.0513) of open pastures and honeylocust silvopastures. Carcass characteristics evaluated did not vary among treatments except hot carcass weight with black walnut having lower weights (P=.0045). Meat quality characteristics did not vary among treatments (P>0.1). Shear force and fat content showed great differences and varied by year (P<0.05). Overall, carcass and meat quality was similar for all treatments showing great promise for silvopastures.
Honeylocust and Black Walnut Tree Products within a Temperate Appalachian Silvopasture
Johnson, Jacob William (Virginia Tech, 2011-02-04)
Incorporating high-sugar varieties of honeylocust (Gleditsia triacanthos L.) or black walnut trees (Jugulans nigra L.) into pasture systems may improve soil and water quality, increase biodiversity, and diversify farm incomes. Studies of productivity and management are needed to understand the trees' potential. Research was conducted in the agroforestry demonstration plots at Virginia Tech's Kentland Farms to 1) estimate both the variability of seedpod yield and nutritive value from juvenile Millwood honeylocust trees, 2) measure changes in nutritive value and digestibility over-winter in Millwood and wild-type honeylocust seedpods, and 3) estimate black walnut biomass productivity, timber quality, nut production, and kernel quality in response to tree density and topography within an emulated silvopasture. Ground Millwood seedpods were comparable to whole-ear dent corn in terms of nutritive value. Both ground pods and seeds were highly digestible (78.7 and 96.3%, respectively) and low in fiber and lignin. Seeds, with over 20% crude protein (CP), have potential as a CP supplement. Millwood trees displayed alternate bearing patterns with 3-yr average yields of approximately 12 kg tree-1. Total aboveground biomass for black walnut trees planted on toe-slopes (109.0 kg) was 72% greater than at back slopes (63.2 kg) and nearly 3-fold more than at shoulder-slopes (37.6 kg). Nut yields ranged from 0 to 7.9 kg of dried, hulled nuts tree-1 year-1. All walnut trees displayed alternate nut bearing patterns and nut production was marked by high variability.
Influence of cultivar, topping height, and harvest treatment on physical and chemical characteristics of flue-cured tobacco
Mullins, Seth David (Virginia Tech, 2006-01-27)
There has been an increased interest among the tobacco industry in the production of tip leaves in flue-cured tobacco. Different harvest treatments of flue-cured tobacco were compared across six cultivars and two topping heights with the objective of identifying tip grade tobacco. Agronomic and cured leaf chemistry data were collected. Cultivar had significant influences on yield, average price, grade index, and value in three growing seasons. NC 71 and RG H51 were the highest yielding cultivars, with grade indices among the highest as well. Increasing topping height increased tobacco yield in two of three years. As topping height increased there was a significant increase in the percentage of tobacco receiving a tip grade. The four harvest treatments focused on the ten uppermost leaves of the plant. Harvest treatments that allowed proper separation of stalk positions (5&5L and 7&3L treatments) resulted in increased yields and tip grades. Harvest treatments that separate upper stalk position tobacco resulted in a higher percentage of tip grades from a tobacco company grader. Chemical analysis identified differences between stalk positions at the top of the plant. In order for cigarette manufacturers to properly blend the tobacco used to make American blend cigarettes, this separation of stalk positions is important. Harvest treatments that combined stalk positions resulted in the loss of these chemical differences. By topping flue-cured tobacco four to five leaves higher than current extension recommendations and separating stalk positions correctly, tobacco growers can meet the crop throw requirements of tobacco marketing contracts.
Land, Labor, and Reform: Hill Carter, Slavery, and Agricultural Improvement at Shirley Plantation, 1816-1866
Teagle, Robert James (Virginia Tech, 1998-10-07)
As one of antebellum Tidewater's most prominent planters, Hill Carter and the world he and his slaves made at Shirley occupy an important place in Virginia history. Few scholars, however, have analyzed their roles adequately. Previous studies' overwhelming concentration on the architectural and material culture history of the plantation has left Carter's role as one of Virginia's preeminent agricultural reformers virtually unexplored. Assuming ownership of Shirley in 1816, Carter quickly established himself as a leading proponent of agricultural improvement, both embracing and building on the ideas of other reformers like John Taylor and Edmund Ruffin. He diversified his crops and changed their rotations, used new equipment and improved methods of cultivation, reclaimed poor or unproductive lands, and employed a variety of fertilizers and manures to resuscitate his soils. Significantly, Carter efforts to improve Shirley transformed not only the physical landscape of the plantation. The changes produced in the work and lives of his slaves also were considerable. This study, then, investigates the relationship between agricultural reform and slavery. Instead of looking at reform in terms of how slavery affected (or inhibited) it, this work argues that reform must also be understood in relation to how it affected slavery, for changes manifested in attempts to improve lands had important ramifications on slave work routines, which, in turn, affected slave life in important ways.
Long-term effects of copper rich swine manure application on continuous corn production
Anderson, Martha Ann (Virginia Tech, 1990-12-17)
Three long-term field experiments were established in the spring of 1978 and continued through 1988 to evaluate corn (Zea mays L.) response to high Cu levels from Cu rich swine manure and CuS0₄ applications. The field research was conducted on soils with diverse properties, i.e., on a Bertie fine sandy loam (Aquic Hapludults), a Guernsey silt loam (Aquic Hapludalfs), and a Starr-Dyke clay loam (Fluventic DystrochreptsTypic Rhodudults). Three treatments in the long-term field experiments on the three soils were a control, annual applications of eu as eu rich swine manure, and annual applications of Cu as CuS0₄ equivalent to that in the manure. After the 11 years, 1109 mt ha⁻¹ of wet Cu rich swine manure were applied for the manure treatment. The Cu rich manure contained an average of 1316 mg Cu kg⁻¹, An average of 325 kg Cu ha⁻¹ added to the soils from the manure application over the 11 years exceeded U.S.E.P.A. guidelines for safe copper loading levels for cropland by 45 kg ha⁻¹. Copper concentrations in corn ear leaves were within the normal range of 3 to 20 mg kg⁻¹ where the 325 kg Cu ha⁻¹ were applied to the soil as either Cu rich manure or CuS0₄. Concentrations of Cu in the grain were also in the normal range of 1 to 5 mg kg⁻¹ where the high level of the two Cu sources was applied to soils. There was no decrease in corn yield on the three soils from application of either Cu source.
Measurement of Phytase Activity in a Clymer Forest Soil Using the TInsP5 Probe
Huang, Zirou (Virginia Tech, 2009-07-20)
Measurement of soil phytase activity (PA) and delineation of the impact of this important phosphomonoesterase on the P-cycling process in soil and sediments suffer from the lack of a reliable assay. A method for measuring PA in soil that promises to be accurate and reliable has been recently published. The method involves the use of a novel chromophoric analog of phytic acid, referred to as T(tethered)InsP5 (5-O-[6-(benzoylamino)hexyl]-D-myo-inositol-1,2,3,4,6-pentakisphosphate). This study was conducted to measure PA in a Clymer forest soil, which contained over twice the amount of soil organic C as previously tested soils, using the TInsP5 PA assay. This investigation specifically addresses: (1) the development of a soil dilution technique for determining maximal PA, (2) identification of previously unsubstantiated soil-produced dephosphorylated intermediate probe species, (3) the impact of increasing assay buffer pH on soil PA and (4) testing stability of the probe's amide bond in a highly (bio)active forest soil. PA assays were conducted by measuring dephosphorylation of TInsP5 in citrate-acetate buffered (pH 4.2) active and autoclaved (Control) soil suspensions. Phosphorylated probe intermediates (i.e., TInsP4, TInsP3, TInsP2 and TInsP1) and T-myo-inositol were extracted from samples of soil suspension following incubation. Probe species were quantified using reversed phase high-performance liquid chromatography (RPHPLC) with UV detection. PA was calculated based on a mass balance approach. A soil dilution technique was developed to address the challenge of determining maximal PA in soils containing higher organic matter content. In the initial report on use of the TInsP5 method for measuring PA in soil, two "soil-generated" UV-adsorbing compounds (designated Y and Z) were observed, but never confirmed as probe species. The experimental evidence presented in this report supports inclusion of compound Y as a phosphorylated probe intermediate species (i.e. TInsPy), based primarily on its UV adsorption spectra (diode-array detection analysis). Compound Z could not be substantiated as a probe species based on the evidence presented in this study. PA of Claymer forest soil decreased with an increase in assay buffer pH. Further, the probe's amide bond linkage was stable in a forest soil exhibiting high PA.
No-till establishment of switchgrass and Caucasian bluestem
McKenna, James R. (Virginia Polytechnic Institute and State University, 1988)
Cool-season perennial grass growth is suppressed during hot, dry summers. This "summer slump" reduces the availability of grazable forage. Tall-growing perennial warm-season grasses that produce 65 to 75% of their yield in midsummer may provide needed herbage during this period of reduced cool-season forage production. However, establishment of perennial warm-season species is slow and inconsistent when compared to cool-season species. Before these warm-season species can be relied on for summer forage production, a successful establishment methodology must be developed. A study was conducted to evaluate the influence of atrazine [2-chloro·4(ethylarnino)-s-triazine] and carbofuran on establishment of switchgrass (Panicum virgatum L.) and Caucasian bluestem [Boyhtiochloa caucasica (Trin.) C. E. Hubbard]. Treatments of carbofuran at 0 and 1.1 atrazine/ha placed in the row with the seed and of atrazine broadcast at 0, 1.1, and 2.2 kg/ha were imposed in all possible combinations. Another study investigated the influence of limestone, P, and carbofuran on the establishment of switchgrass. Treatments included carbofuran at 0 and 1.1 kg/ha, limestone at 0 and 4.48 Mg/ha, and P at 0 and 22 kg/ha in all possible combinations. Seedling growth rate, leaf appearance rate, plant height, and leaf elongation rate (LER) of seedlings were recorded. Seedling weight and populations were determined at the sixth leaf stage of development. Yields of forage and botanical compositions were also measured in the establishment year. Establishment was further evaluated with yield measurements the year after seeding. Carbofuran application increased first year yield, seedling weight, population, leaf appearance rate, and seedling growth rate. Atrazine reduced seedling population, weight, leaf appearance rate, LER, and yield. Carbofuran partially moderated atrazine influence. The 2.2 kg rate of atrazine tended to injure the switchgrass more than the Caucasian bluestem. In the study investigating limestone and P, carbofuran increased yield, seedling weight, seedling population, LER, seedling growth rate, and leaf appearance rate. The greatest yield, leaf appearance rate, and LER occurred with applications ofP and carbofuran. Even though initial soil pH was 5.1, limestone broadcast prior to planting did not influence seedling measurements and yields in either year. These plantings were made during 1985 and 1986, which were the driest summers in recent years. In spite of the moisture stress, acceptable stands of perennial warm·season grasses were established in both experiments in both years. Including 1.1 kg granular carbofuran/ha in the row, and broadcast application of 1.1 kg atrazine/ha at planting will improve establishment of perennial warm·season grasses. Where the P levels in the soil are low, a broadcast application of 22 kg P/ha improves chances for successful establishment.
Physiological and agronomic aspects of rice varietal responses to low and high nitrogen management
Joseph, K. D. S. Mervyn (Virginia Tech, 1991-08-05)
Modern rice (Oryza sativa L.) varieties produce very high yields under high input and favorable environments. Limited work has been done to develop plant types suitable for less than optimal environments at moderate N management levels. The objectives of this study were: 1) to examine the relationship between the uptake of N and different leaf characteristics, sink size, and grain yield of three morphologically distinct rice varieties; 2) to examine the CO2 exchange rates (CER) of rice varieties in relation to light, N management, water use efficiencies (WUE), and N use efficiency (NUE): and 3) to determine characteristics of rice varieties that are associated with productive potentials under low N management levels. A greenhouse experiment was conducted in 1989 at Virginia Polytechnic Institute and State University, Blacksburg, VA and a field experiment was conducted in Sri Lanka at two locations in 1990. In the greenhouse experiment three varieties (a traditional, an intermediate, and a modem variety) were grown under four N management (rate and time) treatments: viz 1) a 0 N control, 2) 200 mg N kg⁻¹ of soil split into two applications, 3) 200 mg N kg⁻¹ of soil split into three applications, and 4) 400 mg N kg⁻¹> of soil split into three applications. Competitive use of fertilizer N for the development of either large leaf area or high leaf N content per unit leaf area (LNLA) varied with the rate and timing of N fertilizer application and rice variety. When N supply was limited and early N applications were restricted, the intermediate variety increased LNLA in the flag leaf with little increase in total leaf area of the plant. Specific leaf weight did not differ with N management except for the low value of the N control treatment. Increased N applications reduced stomatal density. Total stomatal number leaf⁻¹ varied little within cultivars indicating that N fertilization enables the leaf to increase leaf area and thereby disperses the fixed number of stomates. Carbon dioxide exchange rates were higher in the flag leaf than lower leaves and were directly correlated to LNLA.
Plant and soil effects from the surface application of poultry litter to unmanaged pasture
Lucero, Daniel William (Virginia Tech, 1994-02-03)
The poultry industry, a vital economic force in Virginia, must dispose of vast amounts of waste, mainly litter (PL) , generated during production processes. This study was conducted to investigate the short-term effects of various rates of PL application, i.e., cumulative 2-year totals of 9.8, 19.5, 29.3, 39.0, and 48.8 mt ha⁻¹, to unimproved pasture. Dry matter yield, N recovery and use efficiency, P recovery and use efficiency, and changes in botanical composition were measured on a mixed species, tall fescue (Festuca arundinacea) and bluegrass (Poa pratensis) pasture. Additionally. the accumulation and movement of P was measured in a Starr clay loam (fme-Ioamy mixed thermic Fluventic Dystrochrepts) by the Mehlich 3 (M3) and Bray 1 (Bl) soil tests. Dry matter yields increased curvilinearly with rate of PL application. This yield increase was attributed to correction of N deficiency in pasture by the PL application. Lower levels of PL increased forage yields in 1992 compared with 1991, due to residual effect of unmineralized N from PL applied in 1991. The PL application rate of 11.4 mt ha⁻¹ in 1991, followed by 8.1 mt ha⁻¹ in 1992 was the most environmentally and economically recommendable rate when compared with inorganic N and P recommended fertilizer rates. Forage yields on this treatment were 21.5 mt ha⁻¹ versus 21. 7 mt ha⁻¹ for the inorganic N and P fertilizer treatment. All rates of applied PL increased the percentage of tall fescue (from approximately 50 percent to > 80 percent) and decreased the percentage of bluegrass in this mixed pasture. Phosphorus from both PL and inorganic sources accumulated in the zone of application. In 1992, the highest rates of PL application had increased M3-extractable P levels by 20 fold over the control (192 mg P kg versus 11 mg P kg⁻¹) and caused movement of P into the 10 to 15 cm soil depth. Levels of P extracted by the M3 and Bl soil tests were highly correlated for both years (r² = 0.96 in 1991 and r² = 0.99 in 1992) but the M3 extracted substantially more P from the surface 0 to 5 cm depth (21 percent in 1991 and 23 percent 1992) while the Bl soil test extracted more P from the 5 to 30 cm soil depth (50 to 66 percent more in 1991 and 20 to 57 percent in 1992). Differences in total acidity and F concentrations account for differences of P extracted by the two procedures. Poultry litter is a suitable source of fertilizer for pasture renovation and production in the Piedmont Region of Virginia.

Browsing by Author "McKenna, James R."

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