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The primary objective of this dissertation is to determine Hispanic consumers’ preferences and willingness-to-pay (WTP) for grass-fed beef. Two hundred and thirty-one Hispanic consumers in four experiment sites in Virginia (Galax, Roanoke, Richmond, and Blacksburg) participated in an experimental economics laboratory procedure. Taste tests and visual evaluations were conducted to understand Hispanic consumers’ sensory preferences for grass-fed beef in comparison to conventional grain-fed beef. A contingent valuation method, Multiple Price Lists (MPL) was used to measure Hispanic consumers’ WTP for grass-fed beef. In the study, MPL was put into a non-hypothetical environment due to real products, real money, and actual transactions involved. A bivariate Probit model was estimated to determine Hispanic consumers’ visual and taste preferences for grass-fed beef and to explore the relationship between their expected and experienced quality of grass-fed beef. A two-step decision process examined Hispanic consumers’ WTP and investigated the factors influencing their valuations on grass-fed beef. Approximately 50% of Hispanic consumers sampled preferred grass-fed to conventional grain-fed beef steak and the vast majority of grass-fed preferring consumers were willing to pay a price premium for it. Hispanic consumers were able to distinguish the appearance and taste between grass-fed and conventional grain-fed beef steaks. A positive correlation between visual and taste preferences for grass-fed beef was captured. / Ph. D.

Experiments were conducted to study the effect of gibberellic acid on palatability and digestibility of two grasses, orchard grass and Kentucky 31 fescue. The GA was applied as a spray, except one granular application, at rates of 18 to 72 gm./A. Sheep were used to test the grass for palatability and digestibility. In addition to proximate analysis of grass, data were obtained on soluble carbohydrate, cellulose and lignin contents. Chemical composition of orchard grass was not affected by GA treatment. The most consistent effect of GA on the chemical composition of fescue was a depression of protein content. Ash content was decreased slightly, but consistently. GA increased crude fiber in two experiments; did not affect it in three. Nitrogen free extract was increased slightly in three of the five tests. Cellulose was increased by GA in the summer and fall of 1960, but not in the spring. Lignin was increased in the spring of that year and decreased in the summer and fall. Ether extract and soluble carbohydrate contents were not consistently affected by GA. In general, chemical changes by GA were less than 5%. Orchard grass palatability was improved by GA. In two out of three trials with Kentucky 31 fescue, consumption of GA treated grass was about 38% less than for the control. Irrigation increased palatability, probably due to a large difference in moisture content of the grass. No chemical differences observed were consistently related to selection of grass by the sheep. Digestibility of dry matter in grass tended to be decreased by GA in four out of five experiments. These depressions were less than 5% and in only two cases were they significant. Digestibility of protein, crude fiber, nitrogen free extract and cellulose tended to be decreased and ether extract was made more digestible by GA. Due to the small changes in both digestibility and chemical composition caused by GA no clear-cut explanations could be given for the reduction of digestibility. The effect seems related to a slight protein reduction and in some cases to an increase in crude fiber and cellulose. Although a number of factors which may affect GA response (time after application, growth rate of grass, light intensity, temperature, etc.) have not been studied, it seems unlikely that this growth regulator will exert much effect on the factors controlling digestibility of grass under field conditions. The effect on palatability is more pronounced, but not consistent. The digestibility of fall grown fescue increased with age. This increase probably resulted from accumulation of soluble carbohydrates and decreases in crude fiber, cellulose, and lignin contents in the grass. / Ph. D.

Tall fescue (Festuca arundinacea Schreb.) has great utility as a low maintenance turfgrass in the northern and transition zone regions of the United States. However, it is difficult to successfully maintain tall fescue of high quality over consecutive summers because of its susceptibility to the fungal pathogen Rhizoctonia solani, which causes the disease brown patch. Not only is brown patch aesthetically unpleasing in a stand of tall fescue but it can also thin out the turf and allow for the encroachment of undesirable weedy species. Cultivar selection, cultural practices, mixing turf species and timing of pesticide applications all can impact the epidemiology of brown patch in tall fescue. Research was conducted in tall fescue to quantify chitinase activity in different cultivars, elucidate the impact of mowing height and nitrogen fertility on brown patch and bermudagrass (Cynodon dactylon L.) encroachment, to evaluate seeding mixtures of tall fescue with hybrid bluegrass (Poa pratensis x Poa arachnifera) on diseases and weeds as well as measuring the impact of the herbicide bispyribac-sodium on brown patch. Chitinase activity was greater in the tall fescue cultivar that was less susceptible to brown patch. In the mowing-fertility studies, cutting tall fescue at 10 cm generally reduced brown patch and bermudagrass encroachment compared to 6 cm. Mixing hybrid bluegrass with tall fescue reduced disease and weed species infestations compared to tall fescue alone. Applying bispyribac-sodium earlier in April resulted in less brown patch and better weed control compared to application in May. Based on this research brown patch severity and subsequent weed species infestations can be reduced by selecting a tall fescue cultivar with a high basal level of chitinase, mowing it at 10 cm and mixing it with a hybrid bluegrass cultivar. / Ph. D.

Field research was conducted to investigate the impact of vegetative filter strips (VFSs) on surface runoff water quality and to determine if this impact decreases with time. The field research provided information for the development and testing of a model to describe the dynamics and fate of nitrogen (N) in VFSs. The experiment had a completely randomized design, with 3 treatments and 2 replicates per treatment. The treatments were 3 VFS lengths: 0, 4.27, and 8.5 m VFSs. The distribution free Kruskal-Wallis test indicated that the runoff, TSS, NO₃⁻-N, NH₄⁺-N, and TKN yields and concentrations from the 8.5 m VFSs were significantly less (α = 0.05) than the influent values. The TSS and NH₄⁺-N yields and concentrations and the TKN concentration from the 4.27 m VFSs were significantly less than the influent yields and concentrations. The Mann-Kendall test indicated that the yields of TSS, NO₃⁻-N, NH₄⁺-N, and TKN from the filters did not significantly increase from 1992 to 1993 and neither did the FTKN yield nor the FTKN concentration from the beginning to the end of 1993. The mean percentage reductions in influent runoff, TSS, NO₃⁻-N, NH₄⁺-N,, and TKN yields from the 8.5 m filters were 73, 91, 79, 86, and 83%, respectively. The mean percentage reductions in influent TSS, NO₃⁻-N, NH₄⁺-N, and TKN concentrations from the 8.5 m filters were 88, 50, 66, and 75%. The mean percentage reductions in influent runoff, TSS, NO₃⁻-N, NH₄⁺-N, and TKN yields from the 4.27 m filters were 43, 83, 55, 40, and 56%, respectively. The mean percentage reductions in influent TSS, NO₃⁻-N, NH₄⁺-N, and TKN concentrations from the 4.27 m filters were 81, 45, 26, and 41%. Based on the information gathered from the experiment results and the literature, a continuous, long-term, field scale model (Grass Filter Strip Model, GFSM) was developed to describe N transport and dynamics in VFSs. The model was based on GRAPH (GRAssed-strip-PHosphorus), a field scale, event-based model that describes sediment and P transport in runoff. The model simulates sediment, nitrate, sediment-bound and dissolved ammonium, and sediment-bound organic N transport during a runoff event. The model simulates the daily percolation and evapotranspiration and dynamics of nitrate, sediment-bound and dissolved ammonium, and sediment-bound organic N in the filter between runoff events. The model predicts the amount of N and sediment exiting the VFSs, and it can be used to estimate the site specific effectiveness and length of VFSs. The model can also be run for an event to assess the effectiveness of VFSs in reducing nonpoint source pollution loading from a single design storm. The model was validated using runoff, sediment, NO₃⁻ and NH₄⁺ yield field data gathered from April to December, 1993. The model predicted reasonably well (within a factor of 2) the cumulative runoff volume and the yields of TSS. NO₃⁻ and NH₄⁺. The model was most sensitive to the runoff rate, depth of the EDI, soil water storage depth, field capacity, and the steady-state infiltration rates. The model was used to determine the minimum length of VFS required for a 1.3 ha field in Georgia to achieve 75% and 40% sediment and nutrient reductions, respectively, over a 10-year period. The model results indicated that a buffer length of 6.3 m was sufficient to reduce sediment and nitrogen losses by the specified percentages. / Ph. D.

In terms of acreage, forage is the number one crop in Virginia. The backbone of these forages has long been tall fescue (Lolium arundinaceum (Schreb.) S.J. Darbyshire). Knowledge of the plant species that make up a pasture and the relative amounts of each species present is important for interpreting potential animal performance. It is also important to know the relative amounts and types of weeds present and to monitor for the presence of poisonous plants or noxious weeds. An experiment was conducted in 2003 through 2005 to investigate botanical composition and yield of "Lakota" prairie grass (Bromus catharticus Vahl.), "Kentucky 31" endophyte-infected (KY31 E+), endophyte-free (KY31 E-), and "Quantum" tall fescue (non toxic endophyte infected) under grazing by stocker steers. Forage botanical composition and yield were determined by clipping three 0.25-m2 areas per treatment replicate. Prior to harvesting, the canopy height within each quadrate was measured with a disc meter. In 2005, productive ground cover was assessed using visual evaluation techniques, point quadrat method, and digital imagery quantified with terrestrial remote sensing. Forages were established September 2002 and grazing was initiated in July of 2003. Experimental design was a randomized complete block with four replications. Averaged over the three years the yield of KY31E+ was higher (p<0.05) than all other treatments. Lakota prairie grass had lower (p<0.05) yields than both KY31 E+ and Quantum tall fescue, however no yields did not differ between Lakota prairie grass and KY31 E-. Our results showed a typical forage distribution curve for all the treatments. Early spring, summer, and fall productivity of Lakota prairie grass was less than all the fescues, thus did not extend the grazing season. Forage persistence was greatest for KY31 E+ and Quantum and lowest for Lakota when averaged over all years. Among sampling methods for ground cover, terrestrial remote sensing was the most accurate, compared with visual evaluation and point quadrat methods. For estimates of all yield indirect methods of assessment had high errors; however the plate meter calibrated by sward density seemed the least variable of the methods tested. / Master of Science

Estuaries, an important facet of coastal regions, are highly productive natural systems, frequently acting as drainage basins for various pollutants such as agricultural runoff. The estuarine grass shrimp, Palaemonetes pugio, has been shown to be a sensitive indicator of pesticide exposure. In this study, emphasis was placed on the quantification of the lethal and sublethal effects of aldicarb on three different life stages of P. pugio. Acute 96-h toxicity tests were conducted with newly hatched larvae, 22-d old larvae and adult grass shrimp to determine lethal toxicant ranges. LC₅₀ values were 85.0 ug/L for newly hatched larvae, 70.7 ug/L for 22-d old larvae and 125.4 ug/L for adults. The impact of aldicarb on specific neurological functions in the grass shrimp was examined using an acetylcholinesterase assay. Acetylcholinesterase (AChE) activity was reduced in the larvae after exposure to acute concentrations of aldicarb. Mean whole-body AChE activity for the newly hatched and 22-d larvae was significantly lower from the controls (P=0.009). Conversely, mean whole body AChE activity in the adult shrimp was not significantly different from the controls at any concentration (P=0.401), although there was a trend towards reduced activity at 50 and 100 ug/L exposures. A behavioral study was conducted to examine the ability of adult grass shrimp to detect and avoid aldicarb-treated seawater. Behavioral responses were measured in a modified steep gradient chamber. A partition divided the chamber, creating three distinct areas: 1) seawater 2) aldicarb-treated seawater and 3) mixing. There were significant differences between the control and exposed adult shrimp in the amount of time spent in the mixing area (P<0.05). Aldicarb exposed shrimp spent, on the average, 20% more time in the mixing area than the controls. Additionally, exposed shrimp spent significantly more time facing downstream, away from the toxicant source (P<0.05). Exposed shrimp displayed increasing hyperactivity and attempted to jump out of the chamber. / Master of Science