Agriculture and Food Systems - Theses
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ItemThe marketing and production of elite-type wool( 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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ItemInternational competitiveness : implications for the Australian citrus industry( 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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ItemFactors affecting fruit set in hazelnut( 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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ItemAgricultural and related education : past, present and future( 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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ItemThe effect of Twospotted mite, Tetranychus urticae Koch, on William Bon Chretien pear and the management of infestation using damage thresholds( 1997)The research program detailed in this thesis was initiated with industry support to study the process of leaf scorch, the effects of leaf scorch on William Bon Chretien (WBC) pear and if possible to develop practical damage thresholds for twospotted mite, Tetranychus urticae Koch, on WBC pear. At the beginning of this research program, leaf scorch regularly defoliated WBC pear trees in Australian orchards infested with twospotted mite. However, little was known about the process of leaf scorch, the factors involved with its development or importantly whether leaf scorch affected fruit yield. Leaf scorch of mite infested WBC pear trees had been observed by pear growers to occur rapidly especially on poorly irrigated trees. Leaf scorch was commonly thought to be caused by leaf desiccation resulting from either water loss from mite-punctured leaf surface or an upset in normal leaf function. As a result of these earlier observations the initial research focused on investigating the relationship between mite infestation and the development of leaf scorch and on monitoring the water relations of mite infested leaves. A glasshouse experiment was conducted to determine whether the water relations of WBC pear leaves were disrupted by mite feeding. The initial results did not confirm this, so other experiments were devised to further study the effects of mite feeding on the water relations of WBC pear leaves. The conclusion of these experiments was that twospotted mite did not affect the water potential or stomatal conductance of whole WBC pear leaves relative to uninfested leaves, even when leaf scorch was developing on the infested leaves. The effect of mite infestation on photosynthesis was also investigated, with only slight reductions recorded on mite-infested leaves. The glasshouse experiments did confirm that leaf scorch developed on mite-infested leaves only and that the level of leaf scorch damage was related to the level and possibly the duration of mite infestation. Reduced irrigation treatments confirmed that water stress significantly enhances the development of leaf scorch damage on mite-infested leaves. The level of leaf scorch on waterstressed trees was typically twice that of fully-irrigated trees, at given levels of mite infestation. This finding supported the earlier grower observations of a link between poor irrigation management and the development of leaf scorch damage and the study of the water relations of infested leaves. Leaf scorch failed to develop on any non mite-infested leaves, even in the reduced irrigation treatments where leaf water potentials were often lower than -2.5Mpa. This confirmed that there was a direct link between twospotted mite and leaf scorch and that a mechanism other than simple desiccation of the whole leaf was involved in the process of leaf scorch. Sensation is a red skinned pear cultivar that is closely related to the green skinned WBC pear. Pear growers had reported that the Sensation pear cultivar failed to develop leaf scorch when infested by twospotted mite, even though it was a closely related cultivar to WBC. Glasshouse experiments were also conducted to determine the differences in the response of the Sensation and WBC pear cultivars to twospotted mite infestation. The experiments concluded that Sensation is tolerant to twospotted mite, with no leaf scorch developing on mite infested Sensation leaves. The results also suggested that leaf scorch could possibly be developing on WBC pear as the result of a localised hypersensitivity response of WBC tissue to mite feeding. The effect of leaf scorch on flowering, fruit set, fruit size and fruit yield of WBC pear was monitored in commercial pear orchards. Late season or premature autumn flowering was observed on trees that were severely defoliated by leaf scorch damage in summer. However, flowering levels in the following spring were similar on all trees regardless of the level of leaf scorch damage that had developed in the previous season, even on those trees that had prematurely flowered in autumn. Fruit set was significantly reduced by up to 80 per cent on trees that were severely defoliated by leaf scorch in the previous season. Fruit size, which normally increases as fruit set decreases, was found to remain static on trees with low fruit set, even when only a few fruits remained on a tree. Fruit yield was significantly reduced on trees that were defoliated by leaf scorch in the previous season, as a direct result of reduced fruit set and the lack of fruit size compensation. The level of fruit set and yield were both responsive to the proportion of leaf area defoliated by leaf scorch in the previous season. This reduction in fruit set and yield was only observed in the year following defoliation and did not carry over to the second or third season. A field experiment was then established to determine if a relationship existed between twospotted mite infestation and the level of leaf scorch that develops on mite infested WBC leaves. The results obtained over two seasons clearly established that a combination of both the level and duration of mite infestation was strongly related to the level of leaf scorch that developed on WBC pear leaves. An index, Cumulative Leaf Infested Days or 'CLID', that combined both the duration of infestation and the proportion of leaves infested with twospotted mite gave the highest correlation with the development of leaf scorch damage on WBC trees. Irrigation treatments were also included in the experimental design and these confirmed that the development of leaf scorch was higher on water-stressed WBC trees compared with well-irrigated WBC trees. At this point, the research program had established in independent experiments both that leaf scorch damage occurred in a predictable response to an index of mite infestation and that the yield of WBC pear is reduced as the level of leaf scorch increases. The results from these separate experiments were then combined to develop preliminary damage thresholds for twospotted mite on WBC pear. The preliminary damage thresholds were set at 5 and 10 per cent of leaf area defoliated by leaf scorch which corresponds to 1500 and 2400 CLID per season, respectively. The preliminary thresholds were then field-tested in a number of commercial pear orchards over a period of three years. An improved mite monitoring protocol was also developed to enable commercial orchard scouts and pear growers to be involved in the field testing of the preliminary damage thresholds. In general, the level of leaf scorch damage that developed in the field testing stage was below or similar to the level that was expected by the CLID thresholds. In only one instance was the level of leaf scorch damage significantly higher than would have been expected given the level of CLID experienced by the trees in the block. An investigation into the irrigation and soil moisture records concluded that an unusually severe water stress had developed in this pear block and that this had enhanced the development of leaf scorch damage. In the first year of the field testing program, the majority of growers used their traditional calendar-based spray program for mite control. By the third year the majority of growers were using the damage thresholds to determine their spray program. This allowed them to optimise the benefit of mite predators, minimise chemical input and avoid significant yield loss as a result of leaf scorch damage. A computer program, 'MiteMaster', was developed for the last season of the field testing program. The Mitemaster program graphically displays the level of mite infestation, the level of beneficial predators of twospotted mite and the level of CLID calculated, and plots these against the damage thresholds. The scouts and growers indicated that the graphic display of data given by the Mitemaster computer program improved their understanding of the dynamics of mite control in their specific pear blocks. At the end of the field testing program the damage thresholds had been successfully validated under commercial conditions. A set of mite management guidelines, the damage thresholds and the updated MiteMaster computer program were released to the Australian pear industry.
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ItemProduction of heavy weight cryptorchid and wether lambs( 1996)Declining Iamb consumption remains a major problem facing the Australian prime Iamb industry. For Iamb to retain its market share and to remain a viable commodity in the future, leaner Iambs must be produced and marketed. Recent industry initiatives therefore focussed upon the production and marketing of Iambs to meet carcass specifications of 18-26 kg with a fat depth of 6 to 15 mm at the GR site. Emphasis was placed upon the production of lean carcasses weighing more than 22 kg, which are otherwise referred to as Elite Iambs. The development of production, management and marketing systems to produce and market Iamb carcasses of Elite Iamb specifications, both domestically and overseas, was the focus of this research program. The major objective of this experiment was to determine the potential of producing high and consistent quality meat from cryptorchid and wether Iambs meeting carcass specifications for Elite Iambs when slaughtered from six to eighteen months of age. One hundred and sixty three second cross Poll Dorset x Border Leicester/Merino cryptorchid and wether Iambs, born in May 1991 at Rutherglen Research Institute, Rutherglen, were grown and managed on annual pasture at an average liveweight of 50 kg prior to slaughter. Lambs were allocated to one of seven slaughter groups and finished every two months from 6 to 18 months of age and the influence of sex, age and nutrition on carcass composition, meat quality attributes and fat quality and consistency of cryptorchid and wether Iambs examined. Cryptorchid and wether Iambs slaughtered from 8 to 18 months of age produced carcasses meeting targeted specifications of greater than 22 kg with 6-15 mm of fat at the GR site. Lambs slaughtered at six months of age did not achieve the target liveweight of 50 kg at slaughter due to poor seasonal conditions which influenced the quality and availability of annual pasture in spring 1991. Cryptorchid Iambs had a lower dressing percentage and produced carcasses with a lower GR measurement than wethers at a cold carcass weight (CCW) of 23.5 kg. Cryptorchid Iambs exhibited growth rate advantages over wethers only when nutrition and seasonal conditions did not limit Iamb growth. When compared at the same fasted liveweight, cryptorchid Iambs deposited less internal fat than wethers. Cryptorchid carcasses also had a lower proportion of subcutaneous fat present on all primals, higher proportions of soft tissue and bone in the hindquarter and the EMA of the M. longissimus thoracis was significantly larger compared with wethers at a CCW of 23.5 kg. The proportion of CCW in the leg, chump and ribloin was not significantly influenced by Iamb sex. Nutritional management of lambs significantly influenced the proportion of subcutaneous fat on all primals. Meat quality was significantly influenced by Iamb sex however results obtained did not suggest that meat from cryptorchid Iamb carcasses was of inferior quality compared with wethers as only small differences in tenderness, intramuscular soluble collagen content, meat flavour, meat colour, intramuscular fat content and cooking loss were found. In addition, age and nutrition significantly influenced meat quality, however, consistent relationships were not found. The incidence of yellow soft subcutaneous fat was higher in cryptorchid Iamb carcasses than those from wethers with cryptorchids also producing subcutaneous fat with significantly higher levels of total unsaturated fatty acids and lower levels of stearic, palmitic and total saturated fatty acids compared with wethers. Age and nutrition also influenced the fatty acid composition of subcutaneous fat with Iambs fed lupins having significantly higher linoleic acid levels in subcutaneous fat. However, the magnitude of these differences did not explain differences found in fat quality and consistency between cryptorchid and wether carcasses slaughtered at different ages. Significant, though small, differences were found due to sex in both the triglyceride and phospholipid components of intramuscular fat. As higher levels of polyunsaturated fatty acids were found in the phospholipid component of intramuscular fat compared with cryptorchids, this may affect the keeping quality of meat from wether carcasses. Finally, although significant differences due to age were found in the fatty acid composition of intramuscular fat, these differences were not consistent with age and more likely reflected differences in nutritional management between slaughter groups. This study demonstrated that cryptorchid and wether Iambs turned off at heavy market weights on an improved plane of nutrition over a 12 month period produced carcasses meeting Elite Iamb specifications and yielded high quality, tender meat.
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ItemEfficiency of nitrogen fertilization of dry-seeded rice in south-east Australia( 1986)The efficiency and fate of fertiliser nitrogen applied to combine-sown rice were investigated in field experiments in which fertiliser timing, water regime and soil type were varied. The information gained was used to predict strategies for optimising fertiliser efficiency using current techniques, and to predict and test improved fertilisation technologies. The stage of crop growth, water regime and soil properties all had large and interacting effects on agronomic efficiency. On an infertile alkaline grey clay soil, agronomic efficiency of urea applied at sowing was very low (8 kg kg-1) compared with later applications associated with continuous flooding (up to 56 kg kg-1). The low efficiency was due to nitrification and subsequent de-nitrification during the flushing period. Nitrogen-15 balance studies indicated that 80% of the urea nitrogen was lost from the soil-plant system. The rapid nitrification rate and high loss of nitrogen on the grey soil contrasted with the very low levels of nitrate and low losses of nitrogen (10-25%) from urea applied to rice growing on an infertile acidic red soil under alternating conditions of saturation and aeration (sprinkler-irrigation). Furthermore, on a fertile acidic red soil in the same region, other authors have measured large yield responses to nitrogen applied at sowing. These differences highlight the need to consider soil properties and water management when attempting to predict optimum fertilisation strategies. Yields of sprinkler-irrigated rice (managed to replace water lost by evaporation) were reduced by more than 50% compared with rice grown under continuous flood. However, this was not due to decreased plant uptake or increased loss of fertiliser nitrogen in the sprinkler-irrigated treatments. The low yields appeared to be associated with plant water stress, decreased nitrogen mineralization (by approximately half) and location of the fertiliser nitrogen near the soil surface where root activity was probably restricted due to inadequate moisture. On the grey soil, maximum agronomic efficiencies occurred with application shortly before permanent flood or at early panicle elongation. Efficiency was doubled when urea was applied before permanent flood compared with shortly after permanent flood. The greater efficiency appeared to be associated with the deeper transport of the applied nitrogen into the soil, and consequently lower losses by ammonia volatilisation and/or nitrification/de-nitrification. However, even with the most efficient fertilisation strategies, plant 15N recoveries were less than 40%, while losses exceeded 20%. When the 15N balance data were considered in conjunction with the agronomic data,. it appeared that it would be possible to further increase agronomic efficiency if plant recovery of applied nitrogen could be increased. In particular, minimisation of losses of nitrogen (via nitrification/de-nitrification) from fertiliser applied before permanent flood was a most attractive option. Potential methods identified for increasing agronomic efficiency by minimising losses of nitrogen applied before permanent flood were deep placement and the use of nitrification inhibitors and slow release nitrogen sources. Several experiments were conducted in an attempt to improve fertiliser efficiency by banding urea and modified urea sources 5-7 cm below the soil surface before permanent flood. Plant recovery of 15N was increased by up to 20% with banding compared with surface broadcasting. The best recoveries were from urea super-granules (USG). An experimental fertiliser rig and a commercial seeder fitted with a triple disc assembly were used to band the fertilisers in the main plots. There was no significant yield advantage with banded urea over broadcast urea applied before permanent flood. The fertiliser rig caused considerable plant damage. Using the triple disc applicator, it was possible to band fertiliser below the soil surface with minimal soil disturbance, and plant damage, but only under i ideal conditions of soil moisture. Furthermore, where the soil surface was dry and cracked, penetration with the triple discs was no greater than the depth of the cracks into which surface applied urea prills would be washed upon flooding. The yield test of USG was unsatisfactory because of the excessive plant damage with this method. With current technology, there appears to be little scope for improving the efficiency of urea applied before permanent flood by mechanical placement below the soil surface.