School of Agriculture, Food and Ecosystem Sciences - Theses

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    Tree growth modelling of Eucalyptus delegatensis (R. T. Bak.) and other eucalyptus species utilising early-aged stand measurements
    Wong, Justin ( 1999)
    Growth modelling methods for Eucalyptus species that can make use of minimal measurement information are scarce but necessary for those involved in small-scale forestry to make informed decisions about investment and management options. A computer program, FARMTREE, is available for evaluating the costs and benefits of trees on farms, however its growth modelling functions could be improved. This thesis achieves this for Eucalyptus delegatensis (R. T. Bak.) and provides a series of stand basal area, survival, diameter distribution and individual tree diameter increment models that could be incorporated into a FARMTREE-like program. While not a major farm forestry species, the models have been related to other Eucalyptus species and when more later-age data become available, the methods used here could be fully applied to more suitable species. A systematic series of growth predictions were made, with estimates from the earlier processes being used in the next. Initially, the Gompertz function was selected as the best of five non-linear equations and used to model stand basal area based on two, early-age measurements, while keeping the asymptotic parameter constant. Survival was modelled using a modified logistic function with basal area and age as the predictor variables. The results from the above procedures were then used to model diameter distributions using a percentile-based parameter recovery procedure. The predicted distributions were assessed by comparing them to the actual cumulative density functions. Comparing the predicted estimates of basal area, mortality and diameter distributions to those produced by FARMTREE showed that the new estimates were better, both for the stands for which the models were developed, and for an independent data set. Individual tree diameter increment models based on distance-independent competition indices were also studied. Overall, the predictions for two-year diameter increment were not as good as for the previously studied areas of growth. This was especially noticeable when observing the results for the verification data set. These poorer results for diameter increment may be because of the less flexible methods used or perhaps partially due to the accumulation of previous prediction errors. The research approaches and functions used are easy to apply, efficient, accurate and require minimal actual growth measurement information. They could be applied to other species in greater detail when more information becomes available and could be incorporated into FARMTREE or a similar package for use by owners and managers of small farm forests with the expectation of providing improved growth predictions.
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    The marketing and production of elite-type wool
    Deane, Paul C ( 1998)
    Merino woolgrowers can maintain and increase technical and economic productivity by genetic improvement in their flocks. In recent years, genetic improvement in the Merino sheep industry has been the subject of considerable contentious public debate - in particular, the selection for sheep with a type of skin called soft rolling skin (SRS). Hence, one aim in this thesis is to explore ways of evaluating the benefits and costs from an innovation in sheep selection aimed at improving, and realising, the genetic potential of the animals in the farm system. At the farm level, proposed changes of introducing genetic material with traits such as high secondary to primary follicle ratios (> 40:1) for each case studies whole farm system, combined with significant extra inputs to the system, illustrated that for these individual farming systems, there was adequate economic and financial reward to implement the proposed change, if the most likely outcomes occur. In year 12 (steady state) both case studies had a real return on extra capital of greater than 23 percent based on the expected scenario. In such a scenario, if the new genetics incur fewer environmental demands than expected, then real return on extra capital for both case studies would be greater than 40 percent (table 4.2). Based on the most likely scenario, the real internal rate of return over 12 years for both case studies, was greater than twelve and a half percent (table 4.3). The variability of greasy wool characteristics creates uncertainty for processors as to the exact characteristics of the fibre in a wool lot. This makes it difficult to accurately predict how a wool lot will perform during the numerous processes required to convert greasy wool to the final product. The variability of the most important greasy wool characteristics, fibre diameter is not objectively available pre-sale in the sale catalogue. The analysis of sales studied for elite-type wools, showed that these wools did not receive significantly higher prices than non-elite type wools with very similar objective measurements. The null hypothesis (H0) tested, was that the price of elite-type wool was the same as the price of non-elite type wool. The alternative hypothesis (Hi) was that the price of elite-type wool would be greater than the price of non-elite type wool. The one tailed T -test (table 3.3) showed that the price of the elite-type wool was the same as the non-elite type wool i.e. the null hypothesis (H0) was accepted.
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    International competitiveness : implications for the Australian citrus industry
    Sibanda, Stephen ( 1998)
    The Australian citrus industry is going through difficult times. This is partly due to world trends in the liberalisation and globalisation process of agricultural markets. The General Agreement on Trade and Tariffs (GATT), which is now represented by the World Trade Organisation (WTO) has opened new avenues not only in terms of market access but also in competition for these markets. Most world agricultural industries, including Australia's, find themselves in this situation. Trade liberalisation, for the citrus industry, does not only mean the opening up of potential markets in previously closed markets, but also the penetration into Australian markets by other foreign exporters of citrus products. This state of affairs requires that the Australian industry be competitive enough in order to maintain and expand both its domestic and foreign market share. The broad aim of the study is to create a framework within which competitiveness of the Australian citrus industry can be analysed. This framework will then be used to assess how international competitiveness has affected the current and historical perspectives of the Australian citrus industry, and whether it competitive or not. In the process, the concept of international competitiveness will be explored, in its broadest sense and as it applies to the citrus industry. Among the theories of competitiveness which are discussed are Porter's, the World Economic Forum's and Fafchamps's, which deal with competitiveness from a nation's point of view. Data on production trends, supply and disposal of citrus by both Australian and Brazilian producers, tariff levels, costs of production and time series data on the Australian citrus financial statistics, are analysed to create a framework within which competitiveness of the Australian industry can be described. Currently, there is a nationwide call by citrus growers for the government to control the amount of Brazilian juice being imported through a return to previous high tariff regimes, or through physical consumer boycotts of non-Australian juice. The main reason for this action being that local producers are being bankrupted by imported juice. This study attempts to discuss such issues and reveal the real causes of the misfortunes affecting the citrus growers in Australia. The study is based on an extensive literature review of the broad concept of international competitiveness and how it relates to the problems presently affecting the Australian citrus industry.
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    Factors affecting fruit set in hazelnut
    Griffiths, Matthew ( 1998)
    Electrophoresis: A simplified method for extracting peroxidase from stem was developed. Polyacrylamide gel electrophoresis successfully resolved peroxidases (EC 1.11.1.7) for use as a character in cultivar identification of Corylus avellana. The technique involved cutting a sample of cambial tissue with a citrus zester. In a microcentrifuge tube the material was submerged in extraction buffer and pounded with a plastic pestle. Of the range of buffer components tested Tris, glycerol, EDTA, PVP-40 & DTT were adopted. When analysing samples from dispersed sites the selection of stem material and its post-harvest care were important factors to consider. A laboratory manual was written to assist other researchers using the process. Hazelnut: A review of cultivar introduction to Australia yielded over 80 names for the past century. Isolated research had taken place in Victoria, Tasmania and New South Wales. An essay on the use of hazelnut as food found three distinct markets where local production could be sold. Peroxidase was used to identify Australian cultivars. Trials were also developed to examine the reproduction of hazelnut. A bibliography of literature was assembled as a reference source for future researchers.
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    Agricultural and related education : past, present and future
    Matthews, Bernadette ( 1998)
    Research funders, providers, educators and agricultural producers were surveyed to obtain their views on the future directions and needs of agricultural and related education. Information was gathered concerning the missions, challenges and likely major changes facing universities and state government agencies associated with agriculture over the next decade. An overriding focus on issues of environmental management and sustainability was evident in answers with a need for closer interaction between providers of education and research and users of knowledge, particularly agricultural producers. The need to attract high performing and motivated students to fields servicing agriculture was highlighted in the stakeholder survey as well as the literature review, and formed part of a second survey. This survey was conducted to assess the knowledge and perceptions of students' concerning agriculture and the various careers available in agricultural and environmental fields. Year 10 Victorian students from both metropolitan and non-metropolitan regions were surveyed as it was considered that they were at the stage of making first subject choices towards future career paths. A review of changes occurring in the land grant colleges of the United States and similar institutions in Scotland indicated concerns in similar areas. It was concluded that, in common with the United States, existing provision of educational services is failing to meet current expectations of producers in terms of their need for information, creation of learning environments and involvement in decision making of educational providers. It was also noted that the development of an education/research provider partnership with industry was seen as a logical outcome of current debates by some persons from each of the employment categories surveyed. The student survey showed that a greater number of non-metropolitan students had considered a career in agriculture than metropolitan students. It was also found that the most important influence on student knowledge about agricultural careers came from parents, school, and the media; that overall student knowledge of the various careers available to graduates of agricultural science was limited, and where such knowledge existed, it was biased by misconceptions of the role and activities of agricultural scientists. Furthermore students placed great importance on high paying careers, yet did not consider careers in agriculture to be high paying. It was therefore determined that more work needs to be conducted to increase the profile of the variety and activities involved in careers available in agricultural and related areas. The two surveys indicated need for change in Australian agricultural and related education, in similar directions to changes being debated in the United States and elsewhere. This was found in particular with respect to a stronger natural resource management or an environmental approach to agriculture and related education, and enhanced information exchange between industry, and agricultural education and prospective students.
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    Factors influencing the germination, establishment and seed production of weeping grass (Microlaena stipoides)
    Chivers, Ian Harold ( 1998)
    Weeping grass (Microlaena stipoides (Labill.) R. Br. var stipoides) is an Australian native grass of widespread occurrence throughout Australia. It is a perennial, cool-season grass which produces slender rhizomes and remains green throughout the year producing high quality forage (Willis, 1970; Mitchell, 1994). It occurs naturally in a number of habitats from damp grasslands to heath, woodland and forest as well as shady parts of lawns and gardens. It is considered as having potential in the fields of amenity turf, grazing and revegetation since it produces green foliage all year, is tolerant of close grazing or mowing, acid soils, drought and shading, amongst other factors. Commercial production of weeping grass is desirable in order to make this grass available to the broader market. However a number of factors need to be considered before full commercialisation of this grass. Harlan (1960) indicated that seed production, seedling vigour and establishment were the critical factors in the successful domestication of a native grass. Aspects of these factors were considered in this thesis. Two experiments were undertaken to address the gaps in knowledge that prevent commercialisation of weeping grass. Experiment 1 considered the establishment of weeping grass and examined the use of pre-emergent herbicides on the seedling stage to determine if selective herbicides exist for this species. This experiment went on to consider the particular requirements for the best germination of seedlings in terms of the depth of sowing, the presence or absence of a mulch and the cleaning of the seed of its lemma and palea. Of the herbicides tested, Trifluralin was shown to be useful for this purpose in both spring and autumn and Pendimethalin was useful for spring applications. The other herbicides tested, Ethofumesate, Dithiopyr and Bensulide were not selective with weeping grass and cannot be recommended for use. For both seed treatments i.e. intact and cleaned, the two most shallow treatments provided the best germination results for the earliest days of assessment. For surface sown seeds the fastest germination was from seed that had been cleaned of its protective lemmas and which had been covered with a mulch. Experiment 2 considered several factors which may have an impact on the seed production of weeping grass. The factors considered were the effect of the accessions, nitrogen fertilizer and irrigation on seed production. It was found that there were significant variations between the accessions of weeping grass in regard to a number of factors related to reproductive growth. The accessions also showed variation in vegetative characters, and these results together highlight the potential for making suitable selections for desired characters from within the weeping grass gene pool. It was shown that weeping grass was strongly responsive to applications of nitrogen fertilizers, with late applications of nitrogen fertilizer promoting late season seed production. In regard to the irrigation treatments that were applied over the summer/autumn period, some accessions were more sensitive than others to the irrigation regime and the production of culms was more dependent upon the season than on soil moisture. However frequent irrigation did increase the number of culms. The irrigation effect on the increase in culm numbers and seed produced was more influenced by the frequency of irrigation than by the absolute amount of irrigation applied, with infrequent irrigation reducing the number of new culms and seeds compared to more frequent irrigation.
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