Browsing by Author "Rayburn, Edward B."

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    Comparison of techniques for estimating pasture herbage mass and productive ground cover for Lakota prairie grass, Kentucky 31 endophyte free tall fescue, Kentucky 31 endophyte infected tall fescue and Quantum 542 tall fescue grazed by stocker steers
    Rotz, Jonathan Daniel (Virginia Tech, 2006-04-10)
    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.
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    A measure of the natural potential of land for supporting deer populations
    Rayburn, Edward B. (Virginia Polytechnic Institute and State University, 1972)
    A model of the inter- and intra-seasonal energy flow through deer populations ,.;as developed through the use of the existing literature. The model was programmed in Fortran IV for computer based use in evaluating the potential biological productivity of land for deer. The model was developed specifically for evaluating land being considered for acquisition for deer-management areas. The model uses "Standard Deer Units" (an integration of climatic, behavior, and range characteristics affecting the energy dynamics of the deer) as a measure of the energy available for the production and maintenance of deer. Estimation of successional changes in cover and forage production are made by use of a flexible statistical distribution model known as a \.Jeibull distribution. Indices of the potential sightable and harvestable deer production are calculated in standard deer units at 5-year intervals over a 50-year planning horizon.
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    Quality and yield of tall fescue (Festuca arundinacea Schreb.) as affected by season, legume combinations and nitrogen fertilization
    Rayburn, Edward B. (Virginia Polytechnic Institute and State University, 1977)
    Quality and availability of tall fescue (Festuca arundinacea Schreb.) accumulated for fall and winter pasture was influenced by starting dates of accumulation, season of growth, and by the addition of legumes. In 1975 and 1976, 60-day regrowths of tall fescue were evaluated (in vivo) for summer quality when fed alone and in 50:50 grass-legume mixtures to sheep. In 1975, 40-day old alfalfa (Medicago sativa L.) growth and in 1976, 60-day old red clover (Trifolium pratense L.) growth were used as legume treatments. In 1976, 60-day old orchardgrass (Dactylis glomerata L.) regrowth was fed alone and in a clover mix for comparison. Tall fescue was accumulated from mid-June, July, August, and September, fertilized with 112 kg N/ha in August, and fed in December to determine the effect of stockpiling date on in vivo quality. The effect of stockpiling date and N fertilization on yield, yield distribution, and chemical quality of fescue in winter were studied. The total digestible nutrient (TDN) content of tall fescue in summer was variable between years (35.3% in 1975 and 52.2% in 1976). Alfalfa (54.9% TDN) was higher in digestibility in 1975 than tall fescue, but red clover (52.6% TDN) and orchardgrass (52.6% TDN) were similar to tall fescue in 1976. There were no significant differences in intake of the forages. There was a consistent, nonsignificant increase in the digestibility of grass-legume mixes over the average digestibilities of the component feeds. The digestibilities of either summer grown tall fescue forage were considerably lower than those of the stockpiled tall fescue forages if accumulated from July, August, or September (60.2%, 61.6%, 61.6% TDN, respectively). June stockpiled forage (56.9% TDN) was lower in digestibility than the other stockpiling treatments but higher than for the summer grown tall fescue. In 1975, the DM intake (% bodyweight) of accumulated forage increased as stockpiling was delayed (June, 2.04% July, 2.41%; and August, 2.52%). In 1976, the digestibilities of all stockpilings were lower than in 1975. Digestibility increased as the accumulation periods were shortened from June to August (June, 52.0%; July, 56.7%; and August, 61.5% TDN) and then decreased for the shortest accumulation period (September, 54.5% TDN). The 1976 August accumulated growth was divided into top and bottom canopy strata; these strata (62.2% and 60.5% TDN, respectively) did not differ significantly in digestibility from the whole canopy (61.5% TDN). Intake in 1976 was not significantly affected by stockpiling periods or canopy strata. The digestible protein (DP) content of tall fescue for all summer and winter treatments was highly correlated to the crude protein (CP) content. There was a decrease in December dry matter (DM) yields as stockpiling and N fertilization was delayed from June to September. Generally, the best yield response for winter grazing occurred when N was applied at the date of stockpiling. Total yields decreased as stockpiling and fertilization was delayed. The highest total yields were obtained by fertilizing with N in June or July. Regrowth yields during summer were highest from early harvests but the yield distribution was shifted by N fertilization. The winter quality of accumulated tall fescue increased as yields decreased with delaying dates of stockpiling and fertilization. Total nonstructural carbohydrates (TNC 88 % of DM) increased from 14.7% to 30.5% in 1975 and from 11.8% to 28.0% in 1976; CP content increased from 8.2% to 15.5% in 1975 and from 8.2% to 13.9% in 1976 when stockpiling and fertilization were delayed from June to September. However, the yield of TNC and CP decreased as DM yield decreased. The relative chlorophyl content increased in canopies with delayed stockpiling and fertilization. Fertilization with N increased forage quality and resistance to early winter freezing. Yield and quality of tall fescue in February was lower than but highly correlated to the December yield and quality.