Fuzzy logic provides a natural way of dealing with models that require the modeler or user to interpret linguistic variables in order to make a decision. This study focuses on employing fuzzy logic methodologies in order to create an Alamo switchgrass ecological site suitability map for the state of Mississippi. The inputs in the model are available water content (AWC), slope, pH, drainage, color, and texture. All variables were examined through the fist six inches (15cm) of soil. These six variables were assigned fuzzy restrictions based on expert knowledge from plant and soil scientists, combined using the fuzzy additive weighting method, then defuzzified using the center of gravity approach. The result of the final model is a switchgrass ecological site suitability model that uses expert knowledge and classifies sites into five linguistic categories.

The dormancy of switchgrass (Panicum virgatum L.) seeds may be broken by a variety of treatments, including after-ripening and stratification. This study was conducted to investigate and characterize more systematically factors affecting both after-ripening and stratification effectiveness, and the aging that can occur concomitantly with after-ripening. More than one year of after-ripening at ambient temperature and humidity was necessary for germination of newly harvested seeds to increase from as low as 5% to around 80%. After-ripening was not accelerated at temperatures above ambient for seeds stored in paper bags, which permitted the loss of seed moisture at the increased temperatures. Both after-ripening and aging accelerated with increases in temperature (5 to 60°C) and seed moisture content (50 to 130 g kg⁻¹), except that there was evidence of a moisture optimum for after-ripening that shifted downward as temperature increased. For many seedlots, storage at 60°C and 50 g kg⁻¹ seed moisture content for about 1 mo broke most of the dormancy and resulted in acceptably low numbers of abnormal (aged) seedlings. Decreases in germinability caused by post-stratification drying of switchgrass seeds (described herein as "reversion", in which the reverted seeds could be made germinable again by further stratification) increased as the desiccation increased. Revertibility decreased as stratification or after-ripening time increased. Stratification and after-ripening worked additively to release switchgrass seeds from dormancy. Reversion (germination with stratification minus germination after stratification followed by drying) may reveal seedlot differences and changes over time and moisture content that can not be seen otherwise. Imbibed, dormant seeds placed at 21 or 30°C were induced into deeper dormancy, as indicated by length of stratification needed to break the dormancy. Dormancy deepened more as storage temperature and time increased for imbibed seeds. There are transitional temperature and seed moisture ranges where opposing processes (aging vs. after-ripening, stratification vs. dormancy deepening) appeared to overlap or surpass one another. Switchgrass seeds, either on a single seed level, or on the population level, responded continuously to changing temperature and moisture conditions. Less aging was observed for switchgrass seeds stored in N₂. After-ripening of switchgrass seemed not to be influenced by N₂ or air. In sum, switchgrass is revealed to be remarkably plastic in its ability to move toward both greater germinability and greater dormancy. / Ph. D.

Switchgrass (Panicum virgatum L.) is an important native warm-season grass for biomass and forage production in the U.S. This research determined the effect of fertilizer type (conventional, manure, and biosolids) and rate on switchgrass biomass yield and forage quality. Fertilizers were added at 0, 33, 67, 100, and 134 kg N ha-1 on established stands of ‘Kanlow’ switchgrass in three northeastern Kentucky counties. Soils across sites ranged from recently cleared forestland (low pH, P, and K) to productive cropland (high pH, P and K). Stands were sampled for forage nutritive value in June, simulating a hay harvest. Nutritive value and biomass yield were sampled in November and March. Results showed a harvest date effect for mean crude protein (CP) of 8.31% in June and 1.16% November and March. There was also a harvest effect for biomass with a mean yield of all harvests of 16.6 MT ha-1 but a N response at only one site. In conclusion, this study suggested that switchgrass may produce adequate nutritive value for dry beef cows in June and fertilizer type and rate may have a limited effect on biomass yields.

Historically, the tallgrass prairie (TGP) was the largest ecosystem in North America, but today only about 10-15% of the original extent exists today. Some areas have experienced more extreme loss, for example in the state of Illinois less than 0.01% of high-quality native tallgrass prairie remains. Non-native invasive species are a recent phenomenon that threatens the integrity of surviving TGP communities. Ecotypes of dominant C4 grasses are the basis of numerous cultivars, many of which are utilized in prairie restorations. In this study, the effects of three invasive species (Bromus inermis, Schedonorus phoenix, and Poa pratensis) on two lowland (`Alamo' and `Kanlow') and three upland (`Blackwell', `Cave in Rock', and `Trailblazer') cultivars of the dominant C4 grass Panicum virgatum were tested. Two simple pair-wise greenhouse experiments were established in which cultivars were sown as a monoculture or as a mixture of the cultivars with one of three invasive species. Pots were subjected to one of two water treatments with three replicates of each treatment combination. Response variables (height, number of leaves, tiller density, and biomass) and resources (soil moisture, soil pH, soil electrical conductivity, and light intensity) were measured. The greenhouse studies showed that response variables were affected by the presence of invasive species and that the time of growth affected resource levels. Resources are allocated to different areas (i.e growth and reproduction) when competition and stress are implemented on the dominant species. This study was the first to experimentally test for the presence of the physiological stress marker, trigonelline, in a prairie grass. Trigonelline was highest in upland cultivars under low moisture and highest in lowland cultivars under low moisture treatments. The results of these greenhouse studies suggest that invasive species may differentially affect cultivars of Panicum virgatum that may be sown in a prairie restoration. Performance of the P. virgatum cultivars was dependent on the timing of growth, the pot size, the invasive species, as well as soil moisture level. Therefore, when choosing a cultivar source for restoration, resources (i.e. soil moisture) should be looked into to maximize the output of the cultivar.

Switchgrass (Panicum virgatum L.) is a candidate bioenergy crop. Somatic embryogenic (SE) calli are used for genetic transformation in switchgrass. A superior switchgrass line, HR8, was developed using recurrent tissue culture selection from cv. Alamo. HR8 SE calli were genetically transformable using Agrobacterium at an efficiency of ~12%. We used HR8 somatic embryogenic calli for genetic improvement of switchgrass. The lignin content of feedstock has been proposed as one key trait impacting biofuel production. 4-Coumarate: Coenzyme A ligase (4CL) is one of the key enzymes involved in the monolignol biosynthetic pathway. Two homologous 4CL genes, Pv4CL1 and Pv4CL2, were identified in switchgrass. Gene expression patterns and enzymatic activity assays suggested that Pv4CL1 is involved in monolignol biosynthesis. Stable transgenic plants were obtained with Pv4CL1 down-regulated. RNA interference of Pv4CL1 reduced extractable 4CL activity by 80%, leading to a reduction in lignin content with decreased guaiacyl unit composition. The transgenic plants had uncompromised biomass yield. After dilute acid pretreatment, the low lignin transgenic biomass had significantly increased cellulose hydrolysis (saccharification) efficiency for biofuel production. Erect leaf is a desirable trait to adjust the overall plant architecture to perceive more solar energy and thereby to increase the plant biomass production in a field population. We overexpressed an Arabidopsis NAC transcriptional factor gene, LONG VEGETATIVE PHASE ONE (AtLOV1), in switchgrass. Surprisingly, AtLOV1 induced smaller leaf angle by changing morphologies of epidermal cells in the leaf collar region, affecting lignin content and monolignol composition, and also causing delayed flowering time in switchgrass. Global gene-expression analysis of AtLOV1 transgenic plants demonstrated an array of genes has altered expressions. Potential downstream genes involved in the pleiotropic phenotypic traits of the transgenic plants are discussed. / Ph. D.

<div>Switchgrass (Panicum virgatum L.) is an important warm-season perennial grass in livestock systems and has been extensively researched as an herbaceous energy crop. Objectives of this series of studies were to compare morphological development, compositional quality, crop growth, and yield of a recently developed biofuel cultivar ‘Liberty’ to an improved forage cultivar ‘Shawnee’ in multiple Indiana environments. Pure stands of each cultivar were sampled in the field at Trafalgar and Roann, Indiana in 2016. In 2017, samples were collected at Trafalgar, Roann, and Lafayette, Indiana. Samples were collected weekly during the early season and every other week in the late season with development determined by use of the Mean Stage Count (MSC) and Mean Stage Weight (MSW) system.</div><div>In the morphological development study, MSC and MSW were linearly related to both GDD and DOY for both years. ‘Liberty’ growth lagged behind ‘Shawnee’ throughout the whole growing season by approximately seven days. Prediction equations for MSC and MSW were developed based on accumulated GDD and DOY for Trafalgar and Roann in 2017. The prediction equations for MSC as predicted by GDD explained from 84 to 93 percent of the variation in MSC across locations for ‘Shawnee’ and between 90 to 94 percent of the variation for ‘Liberty’. For MSW, ‘Shawnee’ and ‘Liberty’ prediction equations explained from 84 to 93 percent and 90 to 95 percent of the variation as predicted by GDD across locations, respectively.</div><div><br></div><div>In the compositional quality study, samples from every other sampling date were ground and analyzed using near-infrared reflectance spectroscopy (NIRS). Increasing nitrogen fertilizer caused a higher nitrogen concentration at a given MSC. The 0 kg N ha-1 fertilizer rate dropped below 10 mg g-1 nitrogen by MSC 2.2, whereas the 134 kg N ha-1 fertilizer rate had greater than 10 mg g-1 until MSC 2.7. ‘Liberty’ had increased Neutral Detergent Fiber (NDF) concentration as compared to ‘Shawnee’. For whole-plant samples, ‘Liberty’ averaged 727 mg g-1 NDF as compared to ‘Shawnee’ which averaged 718 mg g-1. ‘Liberty’ had 18 mg g-1 higher acid detergent fiber (ADF), on average, as compared to ‘Shawnee’. Acid Detergent Lignin (ADL) was not different among nitrogen fertilizer treatments. Stem-plus-sheath material accounted for a higher percentage of NDF, ADF, and ADL, in whole-plants as MSC increased, as compared to leaf blades. ‘Shawnee’ had higher IVDMD as compared to ‘Liberty’ and the biggest differences occurred around MSC 2.9. At MSC 2.9, ‘Shawnee’ whole-plant IVDMD was 448 mg g-1 and ‘Liberty’ whole-plant IVDMD was 430 mg g-1. Whole-plant ash concentration decreased as MSC increased.<br></div><div><br></div><div>For the study that evaluated crop growth and yield, differences in grams m-2, mass tiller-1, and tiller number per unit area were analyzed in response to growing degree days (GDD) and day of year (DOY). Number of tillers had a negative linear response to GDD and DOY for both years, whereas, mass tiller-1 had a positive linear response to GDD and DOY for both years. Grams m-2 responded quadratically to GDD and DOY. Generally, ‘Liberty’ had 20 percent higher mass tiller-1 and lower number of tillers per m-2 at the end of the season as compared to ‘Shawnee.’ Addition of nitrogen fertilizer generally increased mass tiller-1 and grams m-2. Roann, the northern most site, also had highest tiller numbers at the beginning of the season and decreased faster than at the central Indiana sites. ‘Liberty’ yielded 8.8 percent higher than ‘Shawnee’ across locations, nitrogen rates, and sampling years. Addition of nitrogen fertilizer did not conclusively increase yield. Grams m-2, mass tiller-1, and tillers per sample area helped explain some yield differences. For example, ‘Liberty’ had increased yield as compared to ‘Shawnee’, and ‘Liberty’ also had higher mass tiller-1 with no differences in tiller number between cultivars. While additions of nitrogen fertilizer increased grams per tiller, yield was not significantly increased with added nitrogen fertilizer. Therefore, these measures should not stand alone as a predictor of yield differences between cultivars. Switchgrass is a bunchgrass and has inherent difference in numbers of plant and tillers per plant within a plot, which may not be truly represented by one crop growth parameter alone.</div><div><br></div><div>This study confirms that switchgrass has great potential as a forage and biofuel crop in Indiana with low nitrogen fertilizer requirements and high yield. Understanding how switchgrass morphological development, compositional quality, growth, and yield responds in Indiana environments across locations, years, and nitrogen rates will help guide the future switchgrass management decisions of producers and researchers.</div>

Energy availability and environmental issues are of growing concern; nations are striving to use energy more efficiently while at the same time decreasing the negative impacts on the environment. / The objectives of this study are to: (1) establish a supply price for ethanol derived from switchgrass, (2) establish an accounting budget for carbon dioxide during feedstock production and processing into ethanol, and (3) determine the cost/tonne of CO$ sb2$ using this strategy. / Total cost of production of the feedstock for cycles of 5, 10, 15, and 20 years are $357.06/ha ( $32.73/ODT), $337.81/ha ( $30.96/ODT), $331.52/ha ( $30.39/ODT), and $328.47/ha ( $30.11/ODT) respectively. Thus, the approximate cost of producing one litre of ethanol from switchgrass is $0.47/litre. / Overall, the switchgrass-ethanol system is a net carbon sink for all four cycles, and each hectare of swithgrass sequesters between 1.9 and 6.8 tonne of CO$ sb2$ per year. However, this process is not indefinite, and will stop once the soil organic matter reaches an equilibrium. / The current price for gas is $0.24/litre (excluding taxes and profit margins). According to the price differential existing between ethanol and gasoline and the CO$ sb2$ emissions difference between both systems, the cost of sequestering CO$ sb2$ ranges between $83/tonne and $129/tonne, with the adoption of this specific strategy. At the macro level, Quebec and Canada's total carbon dioxide emissions reached 70 million tonnes and 461 million tonnes respectively, in 1991. Thus, displacing fossil-based energy sources (gasoline) with a renewable energy source (ethanol from switchgrass) to reduce those emissions by 20 % by the year 2010, incurs a cost ranging between $1.16 billion and $1.8 billion for Quebec, and between $7.7 billion and $11.9 billion for Canada. (Abstract shortened by UMI.)

Switchgrass (Panicum virgatum), a native warm-season grass, has been investigated as a renewable energy crop that may provide viable wildlife habitat. This study investigated small mammal populations in switchgrass, hay, and corn to assess the relative habitat quality. Four, three-night trapping sessions were conducted at four locations in Kentucky using Sherman livetraps. Trapping occurred in spring (before first hay harvest), summer, fall (before switchgrass and corn harvest), and winter (post-harvest). Relative abundance of small mammals, calculated using a capture per unit effort index (per 100 trapnights), and mean taxonomic richness were used to compare habitats. Switchgrass had a significantly greater mean taxonomic richness than hay but not corn; however, four genera were captured in switchgrass and only two in corn. Switchgrass had a greater relative abundance of small mammals than hay during the summer, and corn and hay during the fall. Vegetative cover was positively correlated with relative abundance of small mammals. No-till corn and three year old switchgrass had a greater relative abundance of small mammals than conventionally tilled corn and two year old switchgrass, respectively. In conclusion, switchgrass stands managed as a renewable energy crop has the potential to be viable wildlife habitat for some small mammal species.

Carbon storage was compared between two perennial biomass energy systems, namely switchgrass (Panicum virgatum L.) and short-rotation willow Salix alba x glaffelteri L.) at 2 adjacent sites, and further compared with a corn cultivation, a 20-year-old abandoned field, and a mature hardwood forest, in southwestern Quebec. Aboveground carbon results indicated that switchgrass and corn had significantly greater carbon levels than willow at the less fertile site, but no significant differences were detected at the more fertile site. Root carbon results indicated that corn had significantly lower carbon levels than both perennial systems to a depth of 30 cm at both sites. However, switchgrass had significantly greater root carbon levels beyond 30 cm compared with willow and corn, and beyond 45 cm compared with the forest and abandoned field. These findings indicate that deep-rooted perennial grasses such as switchgrass have the potential to sequester carbon at deeper soil layers. Soil carbon results showed that at the more fertile site, willow was associated with significantly greater soil carbon levels than switchgrass. Moreover, both perennial crops had soil carbon levels that were greater than for corn, the abandoned field, and the forest. In contrast, at the less fertile site, no significant differences in soil carbon were detected between the various plant systems examined. The results of this study suggest that the perennial energy crops used, when grown on relatively fertile soils, have the potential to substantially increase soil carbon levels compared with conventional agricultural and/or forest systems. Consequently, when these crops are grown on less fertile soils, their added advantage of increasing carbon storage is lost.

This study is part of a larger collaborative effort to determine the overall environmental sustainability of intercropping pine (Pinus taeda L.) and switchgrass (Panicum virgatum L.), both of which are promising feedstock for bioenergy production in the Lower Coastal Plain in North Carolina. We measured soil CO₂ efflux (RS) every six weeks from January 2012 to March 2013 in four-year-old monoculture and intercropped stands of loblolly pine and switchgrass. RS is primarily the result of root respiration (RA) and microbial decomposition of organic matter (RH) releasing CO₂ as a by-product and is an important and large part of the global carbon (C) cycle. Accurate estimates of the two components of total soil respiration (RS) are required as they are functionally different processes and vary greatly spatially and temporally with species composition, temperature, moisture, productivity, and management activities. We quantified RA and RH components of RS by using a root exclusion core technique based on root carbohydrate depletion, which eliminates RA within the cores over time. We determined the relationship between RS, RA and RH measurements and roots collected from the cores. We took fresh soil cores in July 2012 to compare root productivity of loblolly pine and switchgrass in monoculture versus the co-culture. Additionally, CH₄ and N₂O fluxes were monitored quarterly using vented static chambers. Pure switchgrass had significantly higher RS rates (July, August, September), root biomass and root length in the top 0-35 cm relative to switchgrass in the co-culture, while loblolly pine with and without switchgrass had no significant changes in RS and roots. Correlations between RA and roots showed significantly positive correlation of RA to grass root biomass (r = 0.37, p ≤ 0.001), fine (r = 0.26, p ≤ 0.05) and medium root surface area (r = 0.20, p ≤ 0.1). The estimated portions of RS attributed to RA in the intercrop stand were 31% and 22% in the summer and fall, respectively. No significant treatment differences were observed in either CH₄ or N₂O flux. Our study indicates a decrease in switchgrass root productivity in the intercropped stand versus the monoculture stand which could account for differences in the observed RS. / Master of Science