School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemNo Preview AvailableGenetics of resistance to Heterodera avenae in Triticum tauschii and its transfer to bread wheat (Triticum aestivum)(University of Melbourne, 1995)
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ItemSexual dimorphism of the somatotropic axis in growing lambs(University of Melbourne, 1995)
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ItemDrying and treatment of veneer for high-performance panel products( 1995)At the present time, plywood has lost market share to competitors such as waferboard and oriented strand board (OSB). Improvement in plywood production and plywood performance is required to make plywood competitive with other wood based panel products. The objectives of this study are: (1) to examine the possibility of using microwave for drying rotary cut veneer, (2) to investigate treatment methods for veneer both before and after fabrication of panels using diphenyl-methane diisocyanate (MDI), (3) to test the characteristics of veneer and panels visually and mechanically. The experimental (preliminary and main research topics) approach to addressing this question involves investigating the characteristics of high performance panel products. All experimental designs used in this study are factorial ANOVA models for different factorial levels. A one factorial design was used to analyse the effect of moisture content (0% and 10 %) on the % solid MDI uptake of veneer samples, and the effect of % MDI concentrations (100%, 80%, 60%, 40%, and 20%) on the % solid MDI uptake of small cube wood samples. A two factorial design was used to investigate uptake of MDI in veneer and plywood treatments. The variables tested included three concentrations of MDI (50%, 60% and 70%) and three levels of soaking times (5. 10, and 15 minutes). Another two factorial design was used to analyse the effects of five levels of % MDI concentrations (100%, 80%, 60%, 40%, and 20%) and three levels of temperature setting (60 , 100, and 140 C) on the curing time of MDI solution for small cube wood samples. Analysis of the effects of edge sealing (sealed and unsealed) and pressure type (low and high pressure) on the uptake MDI and Copper Naphthenate was analysed using a two factorial design. The study shows that microwave drying of veneer is technically feasible to cope with veneer drying problems, which at the present time poses a "bottleneck" and is the major consumer of thermal energy used in plywood production. Microwave drying is characterised by having low within charge variability in moisture content after drying; no drying defects and has no effect on the glueability of plywood. However, some importance aspects of the use of microwaves should be taken into account- in designing a commercial drying process. These include: the position, condition, type of wave guide covers and the power level of microwave. Microwave power had a significant effect on drying time. The higher the microwave power used the shorter the drying time. The highest uptake of solid MDI in plywood samples was obtained with 70 MDI following 10 minutes soaking (51 kg/m3). This was followed by 60 MDI (45 kg/m3) after 15 minutes soaking and 50 % MDI after 15 minutes soaking (41 kg/m3) respectively. The highest solid MDI uptake in radiata pine veneer was obtained with 70 % MDI following 10 minutes soaking (115 kg/m3). This was followed by 60 % MDI (94 kg/m3) after 15 minutes soaking and 50 % MDI after 15 minutes soaking (71 kg/m3) respectively. Investigation into the curing processes indicated that the best temperature for curing MDI solution was 60 C. Microwave energy could not be applied for curing MDI treated samples. Microwaving resulted in substantial losses of MDI solution from the wood blocks. Pressure impregnation of MDI, increased the uptake of resin compared to soaking techniques. The highest uptake of solid MDI for plywood samples was obtained with 70 % MDI in unsealed samples using high pressure treatment (359 kg/m3). This was followed by the treatment of plywood which had been edge sealed and high pressure treated (208 kg/m3), sealed and low pressure treatment (71 kg/m3) and unsealed and low pressure treatment (51 kg/m3), respectively. The highest uptake of Copper Naphthenate in plywood samples was obtained for edge-sealed and high pressure treatment (0.92 % wt/wt Cu) followed by unsealed and high pressure treatment (0.88 % wt/wt Cu), unsealed and low pressure treatment (0.45 % wt/wt Cu) and unsealed and low pressure treatment (0.51 % wt/wt Cu), respectively. MDI solution applied to plywood and veneers by immersion improved the surface qualities of these products. The surfaces were smoother, more rigid; there was water resistance compared to untreated samples. Water absorption was limited to 8 kg/m3 after 5 minutes exposure compared to 84 kg/m3 for untreated plywood. The average surface hardness of MDI treated veneers (82) was 4 points (in Shore C scale) higher than untreated veneers (78). The greatest hardness was obtained for samples treated with 50 % MDI solution (85), followed by 60 % (83) and 70 % (78) MDI solutions. The average surface hardness of MDI treated plywood using soaking treatment (85) was 6 points higher than untreated plywood (79). When MDI was applied by pressure impregnation surface hardness scores of 90 were obtained. The average shear strength of MDI treated veneer (0.183 kN) is 35 % higher than untreated veneers (0.135 kN). The highest values were obtained for samples treated with 50 % MDI solution (0.202 kN), followed by 70 % (0.178 kN) and 60 % (0.169 kN) MDI solutions. The average shear strength of MDI treated plywood using soaking treatment was 0.125 kN. This was 24 % higher than untreated plywood (0.101 kN). This shear strength value is 19 % higher when compared to that for Cu Naphthenate treated plywood using pressure treatment (0.105 kN). It can be concluded that MDI resin can be used to improved the water resistance, surface hardness and strength properties of veneer and plywood. Cu naphthenate (in kerosene) preservative can also be used for treating finished plywood without affecting the strength properties of treated plywood.
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ItemAgroforestry strategies for catchments in the humid tropics( 1995)Catchments in the humid tropics play an important role in the ecosystems and the economies of countries they are in. They are slowly deteriorating because of inappropriate land-use systems being practised by people in them. Agroforestry is seen as a potential land-use system which could help rehabilitate degraded catchments and prevent others from deteriorating. However, selection of appropriate agroforestry strategies to be used for a particular catchment is a problem. The aim of this study was to develop a method that would be able to determine the best combination of agroforestry strategies for a catchment in the humid tropics, that is the one that would yield the maximum net social benefit subject to the constraints of maintaining agricultural yield and net income, keeping erosion within acceptable limits, enhancing soil nutrition, and providing a source of firewood for the catchment users. To achieve this aim, Mt. Masaraga catchment in the Philippines was selected as a case study from which some implications could be drawn that would relate to other similar catchments. Potential agroforestry strategies were presented to the upland farmers in the catchment for acceptability. The selected agroforestry strategies were then evaluated for their capability to prevent soil erosion, to supply firewood, and to provide organic fertiliser for three slope classes. A fuel study was also conducted to determine the fuel consumption of the catchment users. Financial and economic analyses of each selected agroforestry strategy for the three slope classes were then conducted. Linear programming models for the catchment were constructed using average value of the rainfall erosivity index value for the computation of soil erosion. A chance-constrained model which takes into account the probability of rainfall erosivity index value exceeding the average was also constructed. Four agroforestry strategies were found to be acceptable to the upland farmers: contour hedgerow; hedgerow with contour canal; live fences; and combination of contour hedgerow and hedgerow with contour canal. Two models were formulated, a model which assumed that the whole catchment would be converted to agroforestry immediately, and one that incorporated the time of adoption of the agroforestry technologies as a further constraint. It was established that in the Mt. Masaraga catchment, it would be profitable to farmers to adopt agroforestry strategies, but the benefit to society was far greater than to the farmers. The cumulative NPV of the incremental net benefits for the optimum combination of agroforestry strategies for the Mt. Masaraga was P72.4 million greater than if the catchment remained under conventional farming. The chance-constrained model indicated that savings would be even higher if the rainfall erosivity index value in individual years exceeded the average rainfall erosivity index value used in the deterministic model. It was established that the land with steepest slopes should be converted to agroforestry first, because of its ability to reduce the high level of erosion expected on these slopes with conventional farming. More rapid adoption of the strategies resulted in greater savings, indicating that it would be worth spending money on education programs to speed up the rate of adoption. Although these results were specific to the Mt. Masaraga catchment, there is nothing to prevent construction of similar models for similar catchments in the humid tropics, and similar results could be expected.
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ItemA marketing approach to recreation management in national parks( 1995)Recreation managers have always attempted to ensure that resources are used effectively in planning and delivering outdoor recreation opportunities. However the lack of a sound theoretical understanding of management's' role and function in the provision of these opportunities limits the ability of managers to meaningfully evaluate the effectiveness of their actions. Many authors believe that the challenge facing recreation research is the development of a model to provide this much needed theoretical base (Allen 1988, Watkins 1990). Using data derived from a visitor survey conducted at Wilsons Promontory National Park, this study examines the potential of defining and evaluating the role of outdoor recreation management from a market-oriented perspective. The concept of voluntary exchange underpins this perspective. Fundamentally, approaching recreation management from this perspective suggests that effectively providing opportunities for outdoor recreation is not necessarily contingent on fully understanding participants recreation experience outcomes. Rather, what is important, is understanding the nature of the exchange between management and participants and how well management performs in this exchange. The visitor survey principally contained two research instruments, importance-performance analysis (Martilla and James 1977), and recreation experience preference scales (Driver 1977, Driver 1983). This not only enabled the nature of the exchange between management and participants to be investigated, but also provided a means to compare a market oriented approach to outdoor recreation management with the more traditional approaches based on the recreation demand hierarchy. The results identified 13 general dimensions to the recreation opportunity provided at Wilsons Promontory National Park. Three visitor segments were identified in the Park visitor population. Analysis of the components of the recreation opportunity important in producing satisfaction for each of these segments suggests that the role of visitor management at the Park is to deliver recreation opportunities which primarily differentiate along a facility based comfort/asceticism continuum. The study also shows that visitor perceptions of management's performance in the voluntary exchange process can be used to help management ensure resources are used effectively in the delivery of recreation opportunities. The study concludes that a market-oriented approach to visitor management in national parks and outdoor recreation areas has considerable potential. However, further research is required to refine the methodology and techniques explored in this study.
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ItemEffects of metal-contaminated sewage sludge on biological N2 fixation and mineralization of legume nitrogen( 1995)The effects of sewage sludges contaminated with heavy metals on soil biological processes have been studied overseas, but there is little similar data for informative recommendations on sludge reuse on Australian agricultural soils. The effects of metal-contaminated sewage sludge on the symbiotic effectiveness of Rhizobiurn leguminosarum biovar trifolii, legume 12 fixation and N mineralization of legume shoots and soil-sludge organic matter were investigated in soil from a 10 year-old, sludge reuse experiment at Glenfield (NSW); in six agricultural soils (Rutherglen Red podzolic, Goulburn Yellow podzolic, Robertson Krasnozem, Condobolin Red-brown earth, Wagga Wagga Sand, Darlington Point Grey clay) recently-amended with four rates (0, 60, 120, 240 dry sludge tonnes (dst) ha 1) of Malabar sludge; and the Goulburn soil recently-amended with four different sludges (Port Kembla, St Marys, Quakers Hill, Richmond) at rates of nil, 60 and 240 dst ha-1 . However, the recently-amended soils were rapidly-reacted with sludge in seven wet-dry cycles each lasting approximately 7 weeks (6 weeks wet, 1 week dry). The Glenfield treatments, initiated in 1982, involved application of sludge at rates of 0, 40 dst ha -1 y-1 or 120 dst ha' y -1, for five consecutive years, to unlimed (pH 4.4) or limed (2.5 t ha -1, pH 5.1) soil. Total heavy metal concentrations in the Glenfield soil treatments ranged from 120-580 mg kg -1 soil, with a range of individual heavy metal concentrations (mg kg-1 soil): 43-255, Zn; 21-197, Cu; 15-45, Cr; 9-16, Ni; 25-77, Pb; < 0.06-1.9, Cd. In the recently-amended soils, total heavy metal concentrations ranged from 40-1070 mg kg -1 when amended with Malabar sludge and 86-788 mg kg -1 in Goulburn soil amended with the different sludges. Individual metal concentration ranges in soils amended with Malabar were (mg kg -1): 13-481, Zn; 3-236, Cu; 12- 182, Cr; < 3-80, Ni; < 7-80, Pb; < 0.06-5.5, Cd, and in Goulburn soil amended with the different sludges: 31-411, Zn; 23-210, Cu; 11-65, Cr; < 3-36, Ni; 11-65, Pb; < 0.06-5.2, Cd. Symbiotic effectiveness (ISE) of R. tr?folii isolated from sludge treated and control soils, was quantified by the dry matter or N content of seedlings of white (Glenfield) or subterranean (recently-amended) clover produced with only Rhizobium N2 fixation as an N source. The contribution of fixed N to legumes grown in unamended and sludged soil was determined by the 15 N isotope dilution method using annual ryegrass as the reference plant. N mineralization was determined in short-duration (10 d) incubation experiments with soil incorporated with or without lucerne shoots (2 g 100 g-1 soil) at soil moisture contents of field capacity (FC) and full water-holding-capacity (FWH). Net mineral N was measured as the sum of NH4+ and N03- . The difference in net mineral N between + lucerne and - Iucerne treatments was taken as the net mineralization of lucerne N termed ? min N. Historic sludge amendment of the unlimed or limed Glenfield soil (maximum heavy metal concentration 500-600 mg kg -1 ) had no adverse effect on ISE compared to unamended soil. The effect of sludge on ISE in the recently-amended soils depended on the soil type and sludge rate. The ISE of R. trifolii surviving in most sludged soils was not reduced at total metal concentrations up to 1000 mg kg -1, however the ISE of these rhizobia was reduced in the Krasnozem and Red-brown earth at sludge rates giving total heavy metal concentrations of 550- 1070 (60-240 dst ha-1) and 668 mg kg -1 soil (240 dst ha-1), respectively. The growth and amount of N2 fixed by white clover in the Glenfield soil was increased by sludge addition, with N2 fixation contributing nearly all (84-98 %) of the clover total N. In the recently-amended experiment, subterranean clover dry weight and total N were increased significantly by sludge amendment of the acidic, podzolic soils and fixed N was increased significantly in the Yellow podzolic. A decrease in N2 fixation was observed in some soils amended with higher rates of sludge. Where a reduction in ISE occurred fixed N was also poor. In other soils where ISE was not reduced, decreased N2 fixation is presumed to be due to either mineral N inhibition, or perhaps to heavy metal effects on nodulation. Mineralization of neither incorporated lucerne nor soil-sludge N were adversely affected by sludge amendment at Glenfield. In the recently-amended soils at FC, mineralization of N proceeded as effectively in sludge-amended soils as in sludge-free soil except that ? min N was slightly reduced in the Red-brown earth and Grey clay at sludge rates of 240 dst ha-1. However, at FWH less mineral N was recovered from incorporated lucerne shoots in sludge-amended soils in the heavier-textured or limed soils, which reduced ? min N relative to the control soil. Thus, there is potential for metal-contaminated sewage sludge to reduce symbiotic effectiveness,N2 fixation and the net recovery of mineral N from incorporated lucerne depending on soil type and sludge rate, but also to benefit clover production and N fixed in other soils
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ItemBoar contact frequency and the timing of puberty in gilts( 1995)The literature relating to the natural attainment of puberty and those factors involved in the early induction of puberty in gilts is reviewed. The first two experiments suggested that motivated/high stimulus value boar(s) may release sufficient stimuli to overcome the seasonal change that mediates the ability of the gilt to attain natural puberty. These experiments also demonstrated that increasing the, frequency of daily boar contact provided sufficient 'cumulative stimulus' to initiate earlier pubertal development, when compared with once-daily contact (P<0.05). In fact, boar exposure three times daily significantly reduced mean gilt age at puberty relative to once-daily boar exposure (183.2 � 2.71 vs. 196.0 � 3.00 days of age respectively, P<0.01). Twice-daily boar contact resulted in an intermediate mean gilt age at puberty (190.3 � 3.01 days). There was also a trend towards a higher proportion of gilts reaching puberty earlier with increasing frequency of boar contact but this effect became less evident after day 20 of commencement of treatment. In a third experiment increasing boar contact frequency to 8 times per day failed to improve the proportion of gilts attaining precocious puberty compared with 4 times daily contact. This suggests that maximum response to boar contact is achieved using 3-4 times exposure per day. The fourth experiment again confirmed that the boar effect is enhanced when boar contact occurs several times each day. It also indicated that transport 'stress' in conjunction with frequent boar contact may further reduce gilt age at puberty. However, transport alone did not significantly advance the timing of gilt puberty attainment. A final experiment suggested that the efficacy of the boar effect can also be maximised by increasing the frequency of boar - contact when large gilt group sizes are involved. However, it may be necessary to increase exposure times (>20 minutes per exposure) to obtain this benefit. No advantage of increasing the number of boars in the exposure groups from 2 to 4 or 6 was apparent in this study.
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