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 (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.

Glyphosate-resistant (GR) Italian ryegrass has been documented in many different countries around the world and has now become a major problem in row crop production areas of Mississippi. Field experiments were conducted from 2006 to 2008 in the Mississippi Delta to evaluate various herbicide and tillage treatment programs for its control. style='mso-spacerun:yes'> Highest level of control and reduction of GR Italian ryegrass biomass was observed with mechanically incorporated as well as surface applied residual herbicides in the fall of the year. style='mso-spacerun:yes'> Control of GR Italian ryegrass was 86-95% with surface applications of clomazone at 0.56, 0.84, and 1.12 kg ai/ha, s-metolachlor at 1.79 kg class=SpellE>ai/ha and KIH-485 at 0.16 kg ai/ha 171 days after emergence. Using a systems approach, preplant incorporated (PPI) class=SpellE>clomazone and/or s- class=SpellE>metolachlor followed by preemergence (PRE) application of paraquat + linuron+ non-ionic surfactant was also found to control and reduce biomass of GR Italian ryegrass.

Bibliography: leaves 213-229. / xxiii, 229, 26 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 2000

With the loss of field burning the amount of crop residue that remains in perennial ryegrass fields has increased. As the amount of crop residue remaining in the field increases so does annual bluegrass. This has resulted in the increased use of herbicides to control annual bluegrass. However, this increased use has also resulted in herbicide-resistant annual bluegrass. Field experiments were initiated in 1997 to investigate residue management options available to growers and their impacts on annual bluegrass emergence. Two sites, Glaser and Wirth, were established with three residue management treatments replicated four times. The treatments included full-straw, bale/flail, and vacuum sweep. Perennial ryegrass seed yield and annual bluegrass seed contamination were evaluated. The vacuum sweep treatment had lower annual bluegrass emergence than the full-straw or the bale/flail treatments during the 1997-98 growing season, for both sites. The fall of 1998 was much drier than the fall of 1997. Annual bluegrass emergence in all plots was lower in 1998 than in 1997 because of the dry conditions. Fall emergence in 1998 was higher in the vacuum sweep treatment than in the other two treatments, which may have been the result of better soil-seed contact in the vacuum sweep treatment. Lower emergence in the spring at the Wirth site compared to the Glaser site may have been due to narrow crop row spacing and cultivar selection, which shaded the annual bluegrass. When growing seasons were combined, there were no treatment differences. However, more emergence was observed in the spring at the Glaser site compared to the Wirth site. Yield was highest for the vacuum sweep treatment at the Glaser site in the 1998-99 growing season. However, competition from volunteer perennial ryegrass in the full-straw and bale/flail treatments could have accounted for this increase. No other differences in yield and no difference in contamination among treatments were observed. However, contamination at the Glaser site was higher in the 1998-99 growing season than in the 1997-98 growing season. Experiments were conducted in growth chambers to determine how differing environmental conditions affect seed germination of diuron-susceptible and diuron-resistant annual bluegrass. Cumulative germination for the susceptible-biotype decreased from 96% to 88% while the resistant-biotype remained above 95% as temperature decreased from 3 0/20 C to 10/2 C. The susceptible-biotype germinated sooner than the resistant-biotype regardless of temperature. The susceptible-biotype had a higher rate of germination than the resistant-biotype at 30/20 C, but not when the temperature decreased to 10/2 C. Germination response to differing matric potentials did not vary much within a biotype for a given soil type and temperature. Therefore, parameters estimated at -1.03 MPa were chosen to contrast susceptible- and resistant biotypes, and soil types, for each temperature. Maximum cumulative germination was greater than 96% for all treatments. When germination on a given soil type was contrasted, differences were only seen for the susceptible biotype vs. resistant biotype on Dayton soil; and the resistant biotype on Dayton soil vs. resistant biotype on Woodburn soil at both temperatures. The lag in onset of germination was shorter for the susceptible biotype on Dayton soil and resistant biotype on Woodburn soil than the resistant biotype on Dayton soil at 30/20 C. At 18/5 C, the lag in onset of germination was shorter for the susceptible biotype on Dayton soil and resistant biotype on Woodburn soil than the resistant biotype on Dayton soil (P = 0.000 1 and 0.0001, respectively). But the rate of germination was faster for the resistant biotype on Dayton soil than both the susceptible biotype on Dayton soil and resistant biotype on Woodburn soil at 18/5 C (P = 0.02 and 0.0004, respectively). The rate of germination did not differ at 3 0/20 C. When just the soils were contrasted, at 18/5 C all annual bluegrass seeds on the Woodburn soil germinated sooner and the rate of germination was higher than on the Dayton soil. These results indicate that the hydraulic properties of the soils may influence germination. However, this was not observed at 30/20 C. The results suggest that the susceptible-biotype was more sensitive to temperature while the resistant-biotype was more sensitive to moisture. Changing crop management in ways that will reduce annual bluegrass emergence and establishment is needed. By altering management strategies, growers may obtain more efficient and effective use of herbicides, while reducing the selection of herbicide-resistant annual bluegrass. / Graduation date: 2000

Perennial ryegrass is an intensive, temperate pasture grass that responds well to applied fertiliser. The purpose of this project was to study the effects of fertiliser on the productivity and quality of perennial ryegrass in KwaZulu-Natal and how this impacts on animal intake. It was hypothesised that over-application of fertiliser to a perennial ryegrass pasture would negatively affect the quality of the herbage for grazing by dairy cattle and that intake would be affected. Thus the project aimed to assess the effects of applied fertiliser on yield, quality and intake of an established perennial ryegrass pasture. The trial consisted of a set of six separate experiments. Each experiment focused on the interaction between two of the major nutrient elements nitrogen (N), phosphorus (P), potassium (K) and sulphur (S). The experiments (NxP, NxK, NxS, PxK, PxS and KxS) were managed separately to avoid possible transfer of nutrients during grazing, which would result in the contamination of treatments. Each factor had three levels (low, medium and high), giving a total of nine treatments per experiment. Each of the experiments was replicated three times in a randomised block design. Increased fertiliser N application rates increased perennial ryegrass yield with a pattern of diminishing return, where split applications above 40 kg N ha-1 produced smaller increases in yield when compared with the response at lower applications of N. Applied P, K and S did not affect yield, suggesting that even the lowest application levels were sufficient to not limit production. Nitrogen application affected apparent intake, but it is suggested that this is due to the yield effect rather than a direct effect of N on apparent intake. The application of P, K and S did not affect apparent intake. Results from this study showed that the quality of perennial ryegrass herbage, especially in terms of feed value to dairy cows, can be significantly affected by applied fertiliser. The extent of the response was affected by sampling date (i.e. time of year) and this must be taken into account when planning a fertiliser management strategy. This is particularly so with respect to N fertiliser recommendations. Crude protein (CP) content of herbage increased with increasing levels of applied N and the extent of the response was influenced by season. P, K and S did not affect CP concentration in herbage, except in the PxK experiment where increased levels of K lowered herbage CP. Applied N considerably increased the concentration of non-protein nitrogen (NPN) in perennial ryegrass herbage. P and S did not affect NPN levels, whereas applied K decreased NPN content in the iv NxK and PxK experiments. Non-structural carbohydrate (NSC) content of herbage was decreased by applied N but was unaffected by applications of P, K and S. Neither neutral detergent fibre (NDF) nor acid detergent fibre (ADF) was affected by applied fertiliser. In this study herbage P declined and herbage Ca increased with increasing levels of applied N. The addition of fertiliser K resulted in lower herbage Ca values. There was no herbage S response to applied fertiliser in this study. Classification and regression tree (CART) analysis identified the primary determinant of apparent intake in experiments containing N as a factor as the amount of material available to be grazed and that NSC, NPN and ADF are also determinants of apparent intake. Cows do not regulate diet choice within the short-term time frame of a meal. Thus intake is determined by short-term needs rather than by meeting long-term nutrient requirements. Fibre creates physical fill within the rumen, thus restricting intake. High NPN content is associated with high nitrate values. The reduction in intake of herbage with high nitrate content may be due to reduced palatability or to a negative feedback system limiting the intake of nitrate and ammonium. Increased NSC content is associated with increased intake, possibly through the effect of sugar on herbage palatability.

Thesis (M. Sc.)--University of Canterbury, 2007. / Typescript (photocopy). Includes bibliographical references (leaves 107-118). Also available via the World Wide Web.

Thesis (M. Agr. Sc.) -- Lincoln University, 2008. / Also available via the World Wide Web.