Veterinary and Agricultural Sciences Collected Works - Theses

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    The effect of Bonzi (Paclobutrazol) on height and flowering of the paper daisies Rhodanthe chlorocephala subsp.rosea and Rhodanthe manglesii
    Pantzopoulos, K ( 1994)
    The pink paper daisies Rhodanthe chlorocephala subsp.rosea and Rhodanthe manglesii are Western Australian wild flowers bush harvested as cut flowers. They produce numbers of showy, long lasting inflorescences at the tips of 50 to 60cm tall stems in spring. The growth retardant Bonzi(R) (paclobutrazol) was applied to both species as soil drenches or whole plant sprays alone or combined seed soaks and drenches. The retardant was applied at various concentrations and times, to determine if plant height could be reduced for pot plant production. Growth was measured weekly and recorded on a graph of maximum/TinimuT desired height (20-30cm). After initial treatments on week 4, all treatments were applied using Graphical Tracking techniques, that is, when actual growth deviated above the maximum height line. Plant height was suppressed with all applications of Bonzi(R) (paclobutrazol). Increasing both the rate and number of applications of BonznK)(pac1obutrazo1) led to an increase in shoot suppression, flowering time and number. The combined seed soak (400ppm Bonzi(R)) and multiple drench application (Bonzi(R) 4mg ai/pot x 3) was most effective in suppressing shoot elongation of R.chlorocephala subsp.rosea with plants 41% shorter than untreated plants. lowering was delayed and numbers reduced, but the compact plants had sufficient numbers of flowers at the end of the trial period to appeal to consumers. Bonzi(R) caused very noticeable delays in flowering in all treated Rhodanthe manglesii plants. The 4mg drenches, (4mg ai/pot x 3) gave the most satisfactory result producing plants 38% shorter than untreated controls but some pots had not flowered by the termination of the trial. The best results, in respect to height, were again the combination seed soak plus drench, with only a single 4mg drench application required to reduce height by 48%, but germination was suppressed excessively and flowering was unacceptably delayed. Although growth was suppressed significantly by whole plant sprays none were saleable due to the unsightly chlorotic foliage effects on both species.
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    Taylors Creek revegetation analysis of plant establishment
    Shaw, P. ; Thorpe, S ( 1988)
    Plant survival data was collected from parts of the Taylors Creek revegetation site approximately eighteen months post planting to determine the overall percentage survival rate of all species in the sample and the percentage survival rate of each species in the sample. This data is used to consider the efficacy of rationale and technique employed in the revegetation of Taylors Creek during 1986. Data was collected by a field survey of a randomly selected sample of planting areas comprising 12 percent of the total planting. Total percentage survival of the sample was 46 percent and the survival of each species ranged from 0 to 100 percent with a survival rate of 58 percent for the group of species best represented in the sample.
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    Conservation analysis of Burnley Gardens
    Ferguson, E. ; Van Berkel, J. ( 1994)
    V.C.A.H Burnley is a horticultural college surrounded by a historic landscape. The gardens were first established by the Horticultural Society of Victoria in 1863 for the acclimatisation of exotic plants especially fruit trees and in 1891 it became a School of Horticulture. A Significant Tree Study and Tree Census provides a current record of the vegetation and its condition. Through a series of maps and verbal descriptions the study depicts the changes that have occurred in the gardens from the 1860s to the present culminating in a Statement of Significance. To ensure the historical integrity of the gardens remains intact, a conservation policy has been formulated which has guided the development of the management recommendations.
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    The Burnley Garden conservation plan 1939-1999
    Hipwell, Linda ( 1999)
    This report is intended to form part II of a Conservation Plan for the Burnley gardens, which will assist in the conservation, and preservation of the Burnley Gardens located on the Yarra Boulevard, Richmond. The gardens have a long and rich history, the inception of the Royal Horticultural Society in 1863 provided the foundation for the Department of Agriculture. Horticultural and Agricultural practices and principals were taught for many years at Burnley and during this time the gardens have seen change and evolution to today where Horticultural training is practiced. They hold immense social, historical and scientific significance. The importance of this site cannot be underestimated and as a result thoughtful and strategic planning is needed in future management decisions. The Conservation Plan for the Burnley Gardens 1939-1999, forms the main part of this report and follows the internationally accepted Burra Charter in its format and language. This plan collates and analyzes the garden's history, identifies its value, and recommends policies that will both retain the garden's desirable ambience and guide it future use, giving due respect to the evolution of the student teaching component the gardens have fulfilled.
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    Master planning of Burnley campus
    Johnston, A. ( 1994)
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    Investigations of seed production potential of indigenous grassland forbs
    Delpratt, Cecil John ( 1999)
    This study investigated the potential for seed production, ex situ, from a range of forbs that were component species of grasslands and other grass-dominated plant communities in south-eastern Australia. Thirty-five species of native perennial forbs were collected from remnant grass-dominated plant communities in southern and western Victoria. All but one species (Tricoryne elatior, which did not germinate) were amenable to propagation and production in bark-based soil-less growing media in a variety of containers. Of 34 species, 29 (85%) flowered and produced seed within one year of propagation, and all species flowered and produced seed within 3 years. Of 20 species planted into field beds in autumn, 15 established successfully. The species generally were not amenable to spring planting in field beds. There was large variation between species in seed production potential due to differences in the number of flowers produced and the number of seeds produced per flower. Seasonal environmental effects on plant development and seed production were investigated in two studies. Firstly, Bulbine bulbosa and Craspedia variabilis were sown outdoors, in containers, at 12 sequential monthly intervals from 2/4/95 to 10/3/96. Both species established from all sowings but most flower and seed production occurred during spring and early summer, regardless of sowing date. For C. variabilis, sowings in January and February produced the most inflorescences per plant in the following spring. B. bulbosa plants produced visible buds approximately one month later than C. variabilis and were harvested 3 months later than equivalent sowings of C. variabilis. The second study investigated the potential for scheduling `out-of-season' production of seed. Seventeen species (that would normally be propagated in autumn) were sown in a greenhouse, and grown outdoors, on three occasions in late winter and spring (6/8/95, 3/9/95 and 1/10/95). Some plants of all but one species (Eryngium ovinum) flowered by April 1996, with 5 species exhibiting complete flowering in one or more sowings (Brachyscome dentata, Leptorhynchos tenuifolius, Velleia paradoxa, Wahlenbergia luteola, and W. stricto). Most species appeared to flower in response to interactions between cool (< 10 C) and warm (> 10 C) temperatures and to changes in photoperiod. It was concluded that to ensure synchronous flowering and, therefore, the potential for panmixis in out-breeding species, most species should be scheduled for flowering in their 'natural' flowering season. A method for improving the harvest efficiency of Bulbine bulbosa was investigated to replace the need for hand-harvesting of individual capsules. The yield, size and germination capacity of seed harvested from inflorescences that had been detached from the parent plant at a range of maturities, and dried at 20 degrees C, were compared to those of seed harvested from intact inflorescences. Seed yield was highest from intact inflorescences but daily harvests were required and harvests spanned a mean of 33 days per inflorescence, double the time needed for detached inflorescences to release all their seed. There was no significant difference between harvest methods in the number of seeds harvested per capsule, but there was a higher proportion of large seeds harvested from intact inflorescences. Germination was greater than 70% for all harvest treatments after 8 months of dry storage. Harvesting and drying inflorescences when one to three capsules had reached harvest maturity appeared to have the potential to increase harvest efficiency in B. bulbosa. The breeding system of Craspedia variabilis was examined in a greenhouse experiment that subjected inflorescences to one of three pollination treatments (none, hand self-pollination and hand cross-pollination). Cross-pollinated inflorescences produced an average of 301 achenes per capitulum, significantly more than either self-pollinated or non-pollinated inflorescences (19 and 15, respectively). It was concluded that C. variabilis is strongly out-breeding and largely self-incompatible. It was concluded that many perennial forb species were amenable to growth in containers but that seed production potential varied between species. For the genetic diversity sampled from remnant populations to be represented in seed produced in cultivated plants, the seed production system must take full account of the breeding system requirements and seasonal influences on flowering and seed production, for each species.
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    Responses of tree roots to post-planting waterlogging and soil compaction
    Smith, Karen D. ( 1997)
    Plants growing in urban soils are frequently subject to waterlogging and changes in soil strength due to compaction and fluctuations in watertables, and variations in texture and bulk density due to the disturbed nature of urban soils. A waterlogging trial was set up to test the ability of recently planted trees to grow new roots under waterlogged conditions and to recover from this period of waterlogging. Corymbia maculata, Lophostemon confertus, Platanus orientalis and Platanus X acerifolia were subjected to a period of waterlogging and then a recovery phase after waterlogging had ceased. Root length was measured at the end of the waterlogging phase, and at the end of the recovery phase. The different species were found to vary considerably in their ability to tolerate and recover from a period of waterlogging. Waterlogging suppressed shoot and root growth in all species trialed. Corymbia maculata, and Platanus orientalis were able to initiate new roots under waterlogged conditions. Platanus X acerifolia and Lophostemon confertus were not able to do this. Compaction trials were set up to test the hypothesis that trees which are able to establish in urban soils will have a higher than average tolerance to soil compaction and to the higher mechanical impedance and soil strength in dry compacted soils. Compaction Trial A tested the ability of the roots of Corymbia maculata, Lophostemon confertus, Corymbia ficifolia and Agonis flexuosa seedlings to penetrate soil cores compacted to bulk density 1.4 and 1.8 Mg/m3 at 13 % gravimetric moisture content. While roots of all species were able to penetrate the soil at the higher bulk density, total root penetration depth was reduced by 60 % across all the species. Compaction Trial B tested the ability of Corymbia maculata and Corymbia ficifolia to penetrate soil compacted at bulk densities 1.4, 1.6 and 1.8 Mg/m3 at two moisture levels, 7 and 10 % gravimetric moisture. At 7 % moisture, both species were able to penetrate soil compacted to 1.4 and i .6 Mg/m3, but neither species was able to successfully penetrate soil compacted to 1.8 Mg/m3. At 10 % moisture, both species were able to penetrate soil compacted to 1.4 and 1.6 Mg/m3. They were also able to successfully penetrate soil compacted to 1.8 Mg/m3, although with significantly less depth of penetration.
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    Some calculations of potential photosynthetic yield
    Denholm, John Victor ( 1979)
    Detailed calculations of light relations and seasonal potential photosynthesis are carried out for models of leaf canopies of closed trellis orchard design, with the object of comparing the effectiveness of light capture and usage in canopies of various fork angles and various values of leaf area index. It is assumed that all canopies have adequate water, carbon dioxide and nutrients, a condition satisfied in practical orchards. After examination of a very simple model, a detailed model is set up to take full account of direct sunlight, diffuse skylight and light scattered diffusely by foliage. Irradiance at leaf surfaces of various orientations is calculated from first principles, since in a canopy whose geometry is not independent of azimuth there is no straightforward way of assessing diffuse irradiance. An analytical expression is derived for rate of photosynthesis averaged over sunlit leaves randomly oriented in azimuth at any given isotropic diffuse irradiance. The calculated field of photosynthetically active radiation is used to estimate canopy net photosynthesis during the fruit-filling season for peach orchards. In such canopies the foliage-scattered diffuse light is found to make a relatively small contribution (about 10 percent) to net canopy photosynthesis. It is found that for any given value of leaf area index the seasonal potential photosynthesis, whether net or gross, increases as canopy fork angle increases, in the range of angles from 40 degrees to 180 degrees. The estimated absolute harvest yield of peaches in a 60 degree canopy is found to be lower than the mean value of published measured yields by about one standard deviation. Reasons for this are discussed. The low estimated yield does not affect the validity of theoretical comparison between the various canopies. One of several possible causes of an underestimate of potential photosynthesis is neglect of penumbral effects. A theoretical framework is developed for estimation of the error introduced in photosynthesis calculations by the assumption that incident direct solar radiation is a perfectly parallel beam of light. The calculations of Miller and Norman (1971) on distribution of direct sunlight flux density along transects in sunflecks are discussed. The present theory is developed in terms of probabilities of irradiation by full sun and by partially shaded sun and the probability of umbra at any level in a leaf canopy. Analytical expressions are derived for probability density with respect to fraction of the full sun radiant flux density for partial shading by a straight edge, a circular disk, and a thin strip. It is shown that solar limb darkening may be neglected for the present purpose. The geometry of umbra and penumbra due to crossed shading edges is discussed and quantified. The developed theory is applied to hypothetical canopies of randomly dispersed horizontal circular leaves and to randomly oriented and dispersed vertical leaves. A parameter called the characteristic leaf area index is introduced; this parameter, which includes foliage density and leaf dimensions, may be used in assessing the error in estimated canopy photosynthesis due to neglect of penumbra. Application of the theory to the effects of vertical distribution of foliage on canopy photosynthesis is briefly discussed. The underestimate of potential canopy photosynthesis in a peach tree canopy due to neglect of penumbra is found to be of order 5 percent.
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    The dynamics of soil, fertilizer and biologically-fixed nitrogen in soil-plant systems
    Chalk, Phillip Michael ( 1997)
    Nitrogen is a constituent of protein and hence is a key element in plant, animal and human nutrition. Low soil N concentrations and attendant N deficiencies are commonplace in world agriculture. Low protein in much of the Australian wheat crop is symptomatic of the overall low N status of our arable soils, a result of either intrinsic soil infertility or of poor soil management under intensive cereal culture. The most intensive exploitation of natural soil fertility over the past century has been under continuous cereal-bare fallow rotations on the cracking clays of the Victorian Wimmera, the Riverine plains of south-eastern Australia, and large areas of northern New South Wales, south-eastern and central Queensland. Historically, the n reserves of the Red brown Earths of New South Wales and South Australia were similarly exploited. The legume-based pasture ley has been a traditional and important component in the attempt to maintain soil fertility in the agriculture of temperate Australia, but the intensification of cropping in response to economic factors has reduced the benefit of the pasture phase. Consequently, the use of nitrogen fertilizers to alleviate acute N deficiency in our arable soils continues to increase. Soil nitrogen presents a complex chemistry because of the involvement of several discrete phases (organic, inorganic, gaseous) in a multitude of processes which can occur simultaneously, and which can be either chemically, biologically or physically-mediated. Nitrogen is a dynamic element, subject to losses via several pathways, given suitable agronomic, edaphic and environmental conditions. Thus it has often been reported that the recovery of fertilizer N by crops is low, and major research programmes have been directed towards improving the efficiency of N fertilizer use. On the other hand, N can be readily gained by the soil-plant system through the agency of biological N2 fixation, and a great deal of effort has similarly been devoted to identifying constraints and fording ways to maximize this input. The measurement of processes which transfer, subtract or add N to the soil-plant system has been a formidable scientific challenge. Identification and quantification of such processes are required before their role in the system N-balance can be properly assessed, and strategies devised to manage the nutrient more efficiently in agriculture. Much of the work collated in this dissertation was based on this philosophy. The processes which are generally considered to be the most difficult to measure in the field are denitrification, NH3 volatilization and biological N2 fixation. However, on closer examination it becomes apparent that field-estimation of rates of net N mineralization or immobilization and nitrification is equally difficult. (From Introduction)