Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

No description available.

"December 2002" / Corrections on back page. / Bibliography: leaves 118-129. / 129 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Annual ryegrass toxicity (ARGT) occurs in grazing animals following the ingestion of seedheads of the annual ryegrass Lolium rigidum, infested with the corynetoxin-producing bacteria, Rathayibacter toxicus. Breaking the disease cycle, through the use of lines of L. rigidum resistant to the nematode Anguina funesta can be used to reduce th risk of ARGT outbreaks. In L. rigidum, resistance to A. funesta appears to be under the control of two unknown, but complementary genes. This study explored alternate approaches towards the allocation of genotype for lines of L. rigidum with respect to resistance to A. funesta. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2003

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains ix, 134 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

The grazing behaviour and diet selection of a vertebrate herbivore, the domestic sheep (ovis aries L.), feeding in patchy perennial ryegrass (Lolium perenne L.) monocultures was investigated. Heterogeneity or patchiness was created by manipulating (1) the nutritional content of ryegrass, (2) parameters of sward structure e.g. sward height, pseudostem and lamina length, and tiller density, and (3) brightness of ryegrass relative to the background sward. Patches were either fertilised turves transplanted into paddock swards or were created in situ by local fertilisation, trimming etc. The background sward was low in nitrogen (<1.0%N dry weight) compared with average ryegrass leys found on farms in British lowland areas. Sheep preferred to graze in transplanted patches of ryegrass. These patches were structurally similar to the background sward, but were higher in nitrogen content and digestibility as a result of fertilisation. Thus, sheep actively selected more nutritious ryegrass. There was a significant quantitative relationship between brightness and the nitrogen and water soluble carbohydrate content of ryegrass. Darker green ryegrass had a higher nitrogen content and lower water soluble carbohydrate content than lighter green ryegrass. It is suggested that sheep learned to use brightness as a cue in intra-specific forage selection. They had a high preference for short, dark green patches of similar height to the lighter green, background sward. Sheep also preferred to graze in tall patches of ryegrass (>10 cm taller than the background sward) regardless of their nutritional content or brightness relative to the background sward. It is likely that sheep use a multiplicity of physical cues associated with perennial ryegrass in diet selection. The interaction between structural and sward parameters and nutrition content of forage in influencing diet selection requires further investigation. In further experiments, an optimal foraging model, the marginal value theorem was used to make predictions about the behaviour of sheep grazing in monocultures containing highly preferred transplanted patches of tall, fertilised ryegrass. By manipulating the cost of travel between these good ryegrass patches and by detailed measurements of intake within patches by individual sheep, I was able to make quantitative predictions about the time spent grazing in each patch. Travel time and costs were increased by moving good patches further apart and by hobbling sheep to slow down their speed of movement. As predicted by the marginal value theorem, average time spent in a patch was positively correlated with average travel time between patches. For two sheep, the predicted and observed times spent in patches were statistically similar at low travel times, while at higher travel times, observed times were greater than predicted. For a third sheep, all observed times were greater than predicted. Thus overall, there was not a good quantitative fit between the model and the observed behaviour. While incorporation of the difference in the energetic cost of travel relative to that of grazing in a good patch into the model resulted in an increase in predicted optimal patch residence times, the fit between predicted and observed values was not significantly improved. Reasons for this difference between observed and predicted patch residence times are discussed. However, these experiments demonstrated that patch-use foraging models may be more useful than prey models in investigating grazing behaviour of vertebrate herbivores, and that travel time between patches of forage is a previously unidentified constraint of sheep grazing behaviour.

Sod-seeding techniques offer graziers a convenient way to introduce superior grass cultivars into underproductive permanent pastures. Production loss and erosion are minimized. In conjunction with improved grazing management and fertilization, renovation can significantly improve yield and quality of pastures. Existent vegetation must be suppressed prior to introducing new cultivars. This study was conducted on two non-irrigated pastures near Corvallis, Oregon, one dominated by annual grass species and the other by perennial grasses and clover. A split-plot design with four replications on each site was used to compare three seeding methods and either (a) two herbicides following close mowing or (b) close mowing alone. The seeding methods were drilling with an Aerway Seedmatic chisel-type drill, drilling with a Tye double disc drill, or broadcasting seed followed by harrowing. Glyphosate and paraquat were the herbicides used for vegetation suppression. Effect of fertilization was compared to no fertilization. Sod-seeded perennial ryegrass had minimal establishment at the site dominated by annual grass species. An inadequate amount of time was allowed for germination of annual grass seeds before herbicides were applied. Annual grass seedlings suppressed the newly sod-seeded perennial ryegrass. Sod-seeded perennial ryegrass was successfully established at the site dominated by perennial species within one year after planting. Broadcasting followed by harrowing of seed resulted in a higher percentage of perennial ryegrass than either the Seedmatic chisel drill or Tye double disc drill. Sod-seeded perennial ryegrass did not contribute significantly to yield until one year after planting. Glyphosate gave better control of the species present before planting leading to a higher percentage of perennial ryegrass and improved yield compared to paraquat or close mowing alone when seed was broadcast and harrowed. Fertilization of unseeded plots increased yield but was not cost-effective. / Graduation date: 1994

Thesis (M.Ag.Sc.) -- Dept. of Agronomy, Waite Agricultural Research Institute, University of Adelaide, 1978).

Thesis (Ph.D.) -- University of Adelaide, Dept. of Plant Science, 2000. / Bibliography: leaves 213-229.

This thesis contains a literature review of Holcus lanatus and records studies on both the growth and spread of the species and the response of it and of Lolium perenne to several management and edaphic factors. Holcus lanatus is an adaptable, competitive species with ecotypes growing in a wide range of environments. It is valuable on hill land, acid, low nutrient soils and to prevent erosion. Beef cattle grazing it have made greater liveweight gains than on L. perenne. Experiments used plants growing in pots and small field plots. A growth study of spaced H. lanatus plants showed they can produce up to 240,000 seeds, most of which germinated shortly after being shed onto moist soil. Seedlings established poorly in a closed sward. Spaced plants produced runners in autumn whose plantlets established better when plants were cut regularly in spring. Holcus lanatus plants needed vernalization in order to flower. This was enhanced by and to a small extent replaced by short days. When H. lanatus plants in bud were cut, useful summer vegetative regrowth resulted. The New Zealand cultivar Massey Basyn was more productive than Oxfordshire H. lanatus in a pot trial. Holcus lanatus dominated a mixture with L. perenne in a glasshouse experiment, especially under high or infrequent cutting, but it was not so dominant in a field experiment. Cattle treading damaged H. lanatus more than it did L. perenne. Holcus lanatus responded to a high water table by producing adventitious and surface roots. Propyzamide at 2.24 and linuron at 1.12 kg a.i./ha in early summer and asulam at 1.12 or 2.24 kg a.i./ha in early September gave good control of established H. lanatus in L. perenne in preliminary trials. The agricultural significance of these results is discussed.