Switchgrass (Panicum virgatum L.) is a promising bioenergy crop for biofuel production. However, the effects of biosolids application on biomass yield, nitrogen (N) concentration, feedstock quality and theoretical ethanol yield (TEY) are rarely reported in the literature. The objectives of this research were: 1) to compare the effects of biosolids application on biomass yield, N concentration, feedstock quality and TEY, and 2) to compare the effects of harvest frequency on biomass yield, N concentration, feedstock quality and TEY. This experiment began in 2010 and tested four plant available N (PAN) rates of biosolids (0, 153, 306, 459 kg ha-1), one urea rate (180 kg ha-1), and two harvest frequencies (cut once in November or cut in July and November) on a Davidson soil at Orange, VA. Biosolids and urea applications increased biomass yield and TEY across years relative to control, but had no effects on measures of feedstock quality. Inconsistent biomass yield responses to harvest frequency were observed during three years. Cutting once per year consistently increased biomass lignin, cellulose, and hemicellulose concentrations, theoretical ethanol potential (TEP), and reduced N and ash concentrations compared to two cuts. Across years one cut increased TEY by 11% over the two cuts. The results demonstrate that biosolids can be applied as an N source to increase biomass yield and TEY. Two cuts increased biomass yield but reduced TEP, and had inconsistent effects on TEY. / Master of Science

Switchgrass (Panicum virgatum L.) has become an important bioenergy crop. Warm, winter temperatures in the southeastern USA allow for fall establishment and winter growth of cool-season legumes that may provide nitrogen to the spring perenniating crop of switchgrass. Data indicates variation due to year and location, but hairy vetch plots provided a greater nitrogen percentage in the subsequent biomass production of switchgrass. In 2011, switchgrass fertilized with 56 kg ha-1 N was greater than the control and in 2012 it was greater than the 28 kg ha-1 N treatment. Variation around the means prevented clear separation among other treatments. The data also showed that hairy vetch had the greatest volunteer frequency and cover percentage throughout the year. Data from the Dairy Farm showed no differences in yields due to a lack of field management the previous years and only ball clover increased its coverage over time.

Managed loblolly pine (Pinus taeda) stands are common in the southeastern United States and provide young forest conditions for early successional breeding birds. Common pine management practices (e.g. hardwood control) and novel practices (e.g. switchgrass [Panicum virgatum] intercropping), may influence breeding bird use. I evaluated breeding bird abundance, diversity, and resource use within loblolly stands treated to control hardwood species, intercropped with switchgrass, and with no additional management. Hardwood control and switchgrass intercropping both decreased hardwoods and shrubs, and increased forbs. Switchgrass intercropping increased some early successional bird abundances. However, diversity was not different among treatments. Switchgrass intercropping increased 13C:12C in birds and vegetation; both hardwood control and switchgrass intercropping increased 15N:14N in birds and vegetation. Birds moved freely among stands of different ages and management practices. My results suggest these practices improve conditions for some early successional birds and may help maintain ecological value of loblolly stands for birds.

The objective of this study was to develop a research platform using a John Deere 425 Hay Cuber and to evaluate inield densification of grass-based biomass for energy fuel sources. The hay cuber was repaired, modernized, and instrumented to provide a stable test platform on which to quantify and evaluate operating parameters. Bermudagrass was chosen as a model for cubing energy grasses such as Giant miscanthus and switchgrass. Lignin sulfonate binder was added to windrowed bermudagrass at 27.6 kg/tonne (50 lbs/ton) to increase the lignin content to that of energy grasses. The material output from the cuber was collected and separated into cubes and fines to evaluate the effectiveness of densification operations. Bermudagrass treated with binder produced significant regressions that accounted for 83% of variation in production parameters.

The United States has become dependent on nonrenewable resources such as nuclear, coal, and crude oil as major sources of energy and fuel. Ethanol has been identified as a renewable fuel source that may help alleviate this dependence. Recent technological advances have developed a method to produce ethanol from lignocellulosic biomass. The purpose of this study is to determine production and transportation costs of switchgrass, eastern gammagrass, and giant miscanthus using Mississippi and Oklahoma data. This study also estimated the returns above the cost of feedstock for a biorefinery and the incentive package needed to pay for feedstock and construction cost. Results indicate cost difference across species, method of harvest, and location. The biorefinery returns and the incentive package explain the amount of capital needed for a biorefinery to compensate for the cost of feedstock and construction.

Switchgrass (Panicum virgatum) has been widely investigated because of its notable properties as an alternative pasture grass and as an important biofuel source. The goal of this study was to determine soil suitability for Switchgrass in Mississippi. A linear weighted additive model was developed to predict site suitability. Multicriteria analysis and Sensitivity analysis were utilized to optimize the model. The model was fit using seven years of field data associated with soils characteristics collected from NRCS-USDA. The best model was selected by correlating estimated biomass yield with each model’s soils-based output for Switchgrass suitability. Pearson’s r (correlation coefficient) was the criteria used to establish the ‘best’ soil suitability model. Coefficients associated with the ‘best’ model were implemented within a Geographic Information System (GIS) to create a map of relative soil suitability for Switchgrass in Mississippi. A Geodatabase associated with soil parameters was constructed and is available for future GIS use.

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. / Master of Science

Two varieties of switchgrass, Cave-N-Rock and Alamo, were baled into 1.8-m diameter by 1.2-m wide round bales and stored outside for 12 months. String-wrapped bales were stored on sad and net-wrapped bales on rock. Six bales (three-string-wrapped, three netwrapped) were destructively sampled at four, eight, and 12 months. Samples were collected for moisture content and compositional analysis. As expected, there was a large moisture content gradient from the weathered layer to the inner core, depending on drying conditions since the last precipitation. In one instance weathered layer moisture content was three times the core moisture content Netwrapped bales were drier than string-wrapped bales. Negligible dry matter loss (DML) was reported at four and eight months for Cave-N-Rock with DML no greater than 7% after 12 months of storage. Calculated DML was highly variable but no more than 16% of original dry matter after 12 months of storage for Alamo. For one set of six bales (Cave-N-Rock, sampled at eight months), the calculated dry matter loss was negative (meaning the bales gained dry matter during storage). This result is physically impossible and illustrates the difficulty in accurately measuring dry matter loss. DML was less for net-wrapped bales on rock than string-wrapped bales on sod. / Master of Science

Agricultural activities have significant impacts on global biogeochemical cycles, particularly carbon and nitrogen. Conventional row-crop agriculture accelerates the decomposition of soil organic matter, contributing to atmospheric carbon and declining soil fertility. Planting perennial warm season grasses is a useful management alternative to row crop agriculture because these species have been shown to be effective at increasing soil carbon storage and retaining nitrogen. The objectives of this research were to examine how converting row crops to a native perennial warm season grass (Panicum virgatum L., common name switchgrass) influences the recovery of soil organic matter fractions and nitrogen retention within an agricultural watershed in the Shenandoah Valley of Virginia. Soil samples were analyzed for total carbon and nitrogen, three particulate organic matter fractions, root biomass, mineralizable carbon and nitrogen pools, and microbial biomass. Surprisingly, I observed significant declines in bulk soil organic matter and surface particulate organic matter pools following switchgrass establishment. There were no differences in mineralizable carbon and microbial biomass pools between row crop and switchgrass soils, but labile carbon pools and nitrogen immobilization increased as switchgrass stands matured. These results are potentially due to switchgrass litter inputs stimulating microbial communities and accelerating the decomposition of recalcitrant soil organic matter, leading to declines in soil organic carbon stocks. The results from this study will be used to understand the environmental and economic benefits of implementing switchgrass plantings in agricultural watershed as a means to mitigate agriculturally-induced effects on carbon storage and nitrogen retention in soils. / Master of Science

The US Department of Energy has focused research efforts on developing switchgrass into a bioenergy feedstock, helping to offset the use of non-renewable fossil fuels and make the US more energy independent. Bacterial endophytes, which reside inside plant tissues, are proven to increase yield and stress resistance in a number of plants. The primary objective of this dissertation was to explore the use of endophytes to improve biomass yields of switchgrass on lands not suitable for food crops and better understand the underlying mechanisms of the plant-endophyte interaction. Integration of this research into K-12 STEM education to increase interest in plant sciences and create the next generation of scientists with the motivation to help solve the challenges facing society in the twenty first century was the objective of the outreach component of this project. Chapter one demonstrates the ability of Burkholderia phytofirmans strain PsJN to colonize switchgrass and promote plant growth under in vitro (approximately 50% higher), and growth chamber and greenhouse (48.6% higher biomass yields) conditions. The objectives of Chapter two were to determine stand establishment in the field with different nutrient levels. PsJN bacterization positively benefited growth and development of switchgrass seedlings in the field with both low and high nutrient content. Highly significant (p<0.001) stimulation of root and shoot growth, lateral root formation and number of tillers was recorded on soil with low fertility. PsJN bacterization also enhanced biomass accumulation during the two seasons of growth on both poor (p<0.001) and rich (p<0.05) soil, indicating the potential for the use of PsJN in a low-input switchgrass feedstock production system. Chapter three outlines differences in gene expression patterns upon bacterization, between the responsive cv. Alamo, and a non-responsive cv. Cave-in-Rock. Using EST microarrays and quantitative PCR up- and down-regulated genes were identified in both cultivars. One of the key genes identified was a member of the tau class, glutathione S-transferase (GST). GST enzymes are known to be involved in plants responses to stress. Using overexpression and knockout/knockdown techniques we demonstrated that GST is likely involved in the bacterization induced early plant growth promotion in switchgrass. Chapter four describes the potential for the utilization of beneficial bacterial endophytes capable of fixing atmospheric nitrogen in a free-living state in the development of low-input switchgrass feedstock production systems. Sphingomonas sp. strain NSL isolated from switchgrass tissue was able to grow on nitrogen free medium and stimulated growth of switchgrass cv. Alamo under nitrogen deficient conditions. The ability to fix atmospheric nitrogen was also moved to Burkholderia phytofirmans strain PsJN via horizontal gene transfer from the legume nodulating Burkholderia phymatum. The transformed PsJN was able to fix nitrogen and promote plant growth under nitrogen limited conditions. At every step of the research described in this dissertation efforts were made to include its elements into K-12 education. Chapter five describes four case studies aiming at the enhancement of youth interest in plant sciences in the socieoeconomically depressed areas of Southside Virginia. / Ph. D.