School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemThe effect on some milking characteristics of cows of changing the flow rate thresholds of automatic cluster removers in a seasonally calving dairy herd( 2004)An experiment to investigate the effects of altering the end-of-milking point values of automatic cluster removers (ACRs) from 0.40 kg/min (Control) to 0.70 kg/min (Fixed ACR), or 1.00 kg/min (Rising ACR) over an extended period from the peak until the end of lactation of a seasonally calving pasture based herd has been conducted at the Victorian Department of Primary Industries Ellinbank research dairy. One hundred and ninety two cows. and heifers were used in the experiment (64 animals statistically allocated to each treatment group). A comparative analysis of results for each treatment group is presented for average milk yield, average milking duration, average maximum milking duration, average milk flow rate, average peak milk flow rate and udder health. The Fixed ACR treatment reduced the average daily milking duration by up to 7.6%, but only for a small portion of the treatment period. The Rising ACR treatment reduced the average daily milking duration significantly by up to 15.3%, for the majority of the treatment period. The Fixed ACR treatment did not reduce the average daily maximum milking duration whilst the Rising ACR treatment reduced the average daily maximum milking duration significantly by up to 17.9%, for the more than half of the treatment period. A marginal increase in average milk flow rate was observed for the Rising ACR treatment. Even though the Rising ACR treatment began the experiment with higher average peak flow rate for AM and PM it declined less than the Fixed. ACR or Control treatment throughout lactation, providing a mechanism for the, removal of the same amount of milk in a reduced time when compared with the other treatments. However the difference observed in peak flow rates was not statistically significant. No difference was found amongst the treatment groups when analysed for new cases of sub-clinical or clinical mastitis. The geometric mean of individual cow cell counts was significantly reduced for the Rising ACR treatment in the latter stages of lactation. Flow rate curves have been constructed from real milking data and are presented as examples of the large variation of actual- flow rate from a cows udder. The flow rates curves are used to track individual cows through lactation to observe changes in the cow's milking characteristics. Theoretical consideration is given to how particular types, or brands, of ACR operate under various conditions and it is shown that the results from this experiment could be replicated by using other types of ACR if they are managed correctly. This study has shown that significant labour productivity. benefits could be achieved by, increasing the ACR end-of-milking point settings to 1.00 kg/min without impacting milk yield. However, further work is suggested to ensure that udder health is not compromised. This is to certify that the thesis comprises only my original work except here indicated in the preface; due acknowledgement has been made in the text to all other material used; the thesis is 19400 words in length, inclusive of footnotes, but exclusive of tables, maps, appendices and bibliography.
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ItemAn investigation of environmental conditions experienced during the life of high value wood components and products( 2004)The purpose of this project was to collate data on Australian wood products' exports as well as the environmental conditions that these products are exposed to during manufacture, transportation and service. These data are essential for understanding the potential for wood components to `move' in response to periods of drier or more humid conditions than those at the time of manufacture. The knowledge generated will contribute to a subsequent project, whereby a user-friendly tool will be developed to enable for the design and production of appropriate components, joints, adhesives, coatings, and packaging systems that will ensure superior performance of Australian wood products throughout a wide range of climatic conditions. Wood, a hygroscopic material, will undergo changing moisture contents, fluctuating with changes in atmospheric conditions. As a consequence of these changes in moisture content, wood will swell or shrink. For high-value products, these changes can be detrimental to the utility of the product, for example panels can warp, drawers and doors can jam, and glued components can delaminate. Despite the common occurrence of product degrade or failure due to exposure to changing atmospheric conditions, very little effort has been undertaken to quantify the range of expected conditions for Australian exports. Australian forest industries have a long history of export trade in a wide range of products, from woodchips and sandalwood, through to high-value manufactured commodities such as outdoor furniture and assorted flooring products. Current export markets for high-value wood products were found to be predominantly northern hemisphere countries, including United States of America, China (including Hong Kong), Korea, Japan, Europe (including the United Kingdom) and the Middle East. Other regions importing Australian high-value wood products were south-east Asia (Philippines, Indonesia, Thailand and Malaysia), New Zealand and South Africa. A survey was undertaken to determine the range of value-added products currently exported, and it was found that high volumes of flooring, decking, outdoor furniture and kiln-dried boards for furniture and pre-finished flooring products account for the majority of our value-added export effort. There are currently only minor volumes of assembled indoor furniture suites exported from Australia. Wood fibre panels such as plywood, particleboard and medium density fibreboard were outside the scope of this project due to the in-built stability of these products and only solid wood products were considered. Data generated from the survey included the range of timber species used in the manufacture of export products, sawn orientation and typical section sizes used in components. Results from this work showed that the major timbers are: the ash-type eucalypts from south-eastern Australia; jarrah from Western Australia; spotted gum, hoop pine, white cypress, imported kwila, blackbutt, brush box and Sydney blue gum from New South Wales and Queensland. Environmental conditions, especially the combined effect of temperature and relative humidity in microclimates as determined during this research project, can fluctuate extensively during transport from one location to the next. Equilibrium moisture contents (EMC) as low as 5% and as high as 20% were experienced during the shipping of wood products. In addition, the conditions at the place of manufacture (often 10 to 12% EMC) may be vastly different to the environment where the wood products are ultimately placed in service. The in-service conditions for many of our export destinations are between 6 to 9% EMC. This range of conditions, from manufacturing through transportation and in-service, can potentially create problems, due to wood components swelling and/or shrinking corresponding with periods of higher and/or lower temperatures and humidities. Packaging systems incorporating plastic and cardboard were shown to offer some protection against humidity changes. For the Australian wood-manufacturing sector to achieve and maintain a reputation for superior high-performance products in overseas markets, designers and manufacturers will require a clear understanding of the potential effects of changing environmental conditions on their products. When the range of conditions anticipated throughout the service life of an item is combined with data for timber stability, a manufacturer can allow for movement in the design of the item. An understanding of effective packaging systems is also necessary to ensure maintenance of timber moisture content during transportation. The research highlighted the inherent risks of exporting high-value wood products to distant markets and the need for development of a user-friendly tool, which would allow manufacturers to determine appropriate design parameters such as species, dimensions, jointing systems, adhesives, coatings and packaging for export products.
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ItemPrice risk management in the Australian cotton industry( 2004)Over 95 per cent of Australian cotton producers have attempted to manage price risk at some time, through a broad range of management strategies. The findings of this study suggest that the cotton industry has to date, embraced the principals of price risk management more so than other agricultural commodity industries in Australia. Nearly 60 per cent of Australian cotton producers stated that price risk management had a positive effect on their farm business. Findings from the study suggest that price risk management is only one of a suite of business management tools, but when implemented strategically, it can lead to positive outcomes in terms of business planning and ultimately through increased profitability. A lack of understanding of price risk management and, more specifically, recent currency exchange losses and high production risks were the key contributing factors for the 21 per cent of producers who stated that price risk management had a negative impact on their business. Approximately 10 per cent of cotton producers operated dryland production systems. These producers often incurred a broader range of production risks, and the resulting production uncertainty inhibited effective use of some price risk management strategies. One in four cotton producers had an agriculture-related tertiary qualification, yet few (around five per cent) had undertaken any form of specialist price risk management training. While some cotton producers are competent managers of price risk, the primary conclusion from the study is that much of the current uptake and effectiveness of price risk management in the Australian cotton industry generally, is somewhat limited by a lack of producer experience, confidence and understanding of price risk management principles and processes.
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ItemApplications of GIS in community based forest management in Australia (and Nepal)( 2004)Community forestry is now a popular approach in forest management globally. Although local communities have previously been involved in forest management in various minor ways, community-based forestry is very new in the Australian context. Because of the multiple interests of forest users and other community interest groups, a wider range of up-to-date information is being requested in community forestry, than has been used in ‘conventional’ government-based forest management in the past. The overall aim of this research was to explore the potential and constraints for the application of Geographic Information System (GIS) technology in community forest management in Australia and to relate the results also to Nepal. Specific objectives were to: (i) review the applications of GIS in forestry and community forestry worldwide, (ii) determine stakeholders’ views on their requirements for the use of GIS in community-based forest management, (iii) prepare and demonstrate various practical applications of GIS requested by community groups in the Wombat State Forest, (iv) identify the strengths and limitations of GIS in community forestry, and (v) relate findings on GIS applications in Australia to community forestry in Nepal. This study involved a combination of three approaches: review of global literature on GIS, use of GIS and related technologies, and participatory action research. A wide variety of spatial information was identified through community groups as important for community forest planning and management.
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ItemEcology and management of Vulpia spp. G.C. Gmelin in perennial pastures of southern Australia( 2004)Vulpia species G.C. Gmel. cost the Australian wool industry around $AUS 30 million annually in lost production (Sloane et al, 1998). Vulpia provides poor quality forage and replaces other desirable pasture species, thus reducing stock carrying capacity (Code, 1996). In addition, vulpia seed causes vegetable fault of wool, hides and carcasses, and vulpia litter can impede the germination and growth of desirable species because of allelopathic effects (Code, 1996). This weed is prevalent in pastures and cropping regions throughout southern Australia. Presently vulpia is controlled by different methods, including combinations of herbicide application, grazing management, fertiliser application, oversowing competitive pasture species and mechanical defoliation (Michalk & Dowling, 1996; Matthews et al., 1998; Taylor & Sindel, 2000; Dunsford & Morris, 2001). However, greater understanding is required of vulpia ecology and how it spreads, to develop cost effective, sustainable control strategies in perennial pastures of southern Australia. In particular, key questions that need to be addressed are: 1) how do management strategies influence vulpia populations in perennial pastures; 2) what is the effect of neighbour competition on vulpia growth; and 3) how much space is required to sustain a vulpia population? Thus vulpia management studies incorporating varying levels of disturbance and competition in different environmental conditions were combined with canopy gap and competition studies in field and controlled conditions, to investigate factors that influence pasture botanical composition and vulpia population dynamics. The effect of disturbance and competition management treatments on pasture botanical composition was investigated in phalaris (Phalaris aquatica L.)-based pastures in a 575 mm rainfall zone (Ararat) and a 625 mm rainfall zone (Vasey) in western Victoria, between 1999 and 2002. At Ararat, different fertiliser, herbicide (SpraySeed and simazine) and pasture rest treatments were applied. A combination of all treatments was most effective in enhancing the perennial content and in reducing vulpia content, tiller density and seed production. At Vasey, the effect of simazine and ryegrass competition on vulpia content, tiller density and seed production was investigated in set-stocked, strategic and four-paddock rotationally grazed pastures. Although vulpia increased over the duration of the study in all grazing systems, the rate of increase was least in the four-paddock rotation. Simazine initially reduced vulpia content and tiller density, but vulpia rapidly increased and simazine was unable to provide effective control of vulpia. Oversowing ryegrass in simazine treated swards improved vulpia control. These results demonstrate that competition from perennial pasture species is a key factor in controlling the growth of vulpia populations. The dynamics of competition between perennial plants and vulpia were investigated further in a series of field and controlled experiments. Barley grass (Hordeum murinum L.) was included in these studies to compare and contrast the responses of invasive annual grass weed species. In the first of the experiments, the influence of canopy gap characteristics on vulpia growth and survival was investigated in rotationally grazed and set stocked pastures at Vasey. Vulpia and barley grass growth, survival and panicle production were lower under rotational grazing than set-stocking irrespective of gap size, due to greater perennial competition and pasture height, and reduced photosynthetically active radiation in canopy gaps. The estimated critical gap size below which vulpia and barley grass seed production was prevented was approximately 2 cm diameter in both grazing systems. Timing of gap appearance influenced vulpia and barley grass establishment, but not tiller production, dry weight, survival or panicle production. Fewer vulpia and barley grass seedlings established when annual grasses were sown in June compared to April. The linear effect of perennial competition on vulpia growth, survival and seed production was investigated under controlled and field conditions by sowing vulpia seed at a range of distances from established perennial grass plants. While perennial neighbour competition reduced vulpia growth and panicle production, it did not prevent vulpia from producing seed when sown directly adjacent to a row of phalaris or cocksfoot neighbours (Dactylis glomerata L.). Cocksfoot plants suppressed vulpia growth and reproduction to a greater extent than phalaris plants, particularly in close proximity to the perennial neighbour. This was most likely because of cocksfoot plants being more compact, resulting in greater light competition when annual grasses grew in close proximity to cocksfoot neighbours. In addition, vulpia survival was much less under field than controlled conditions, showing that factors other than competition influenced annual grass survival in the field. Based on these results, it is unrealistic to expect that vulpia can be eliminated from pastures in southern Australia because the normal pattern of dry summers depletes pasture density and creates space that vulpia can exploit when soil moisture levels increase in autumn/winter. The critical gap size required to prevent vulpia seed production is small and vulpia populations are predicted to increase even when seed emerges immediately adjacent to perennial neighbours. However, management practices such as pasture rest, rotational grazing, fertiliser application and herbicide application, which increase perennial ground cover and reduce disturbance of perennial species, do allow some control of this weed. In conclusion, vulpia can best be managed in perennial pastures by a combination of increasing fertility levels in rotationally grazed pastures or pastures rested from grazing over summer, applying herbicide as a winter-cleaning treatment, and over-sowing ryegrass or other competitive species to fill in canopy gaps.