School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemEffect of GnRH and production levels on reproduction in dairy cattle( 1990)At 11-13 days after insemination, 1028 dairy cows on 19 farms were treated with an intramuscular injection of 10 ?g of the GnRH analogue Buserelin. Reproductive performance was compared to 1022 control cows receiving a placebo. Cows treated with the GnRH analogue had a reduced number of short interoestrus intervals compared to control cows but there were no significant differences in pregnancy rates to the insemination preceding or following treatment. Calving-to -conception intervals and percent pregnant by the end of mating were also unaffected. There were no differences between treatments in herds of high, average or low pregnancy rates, within different age groups or within different calving to first service intervals. The evidence here suggests that the use of 10 ?g of the GnRH analogue, Buserelin, 11-13 days post-insemination cannot be recommended as a method of improving reproductive performance in dairy herds.
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ItemQuality of goat milk produced in Victoria( 1990)Preparation of quality standards for the developing goat milk industry in Victoria required study of unknown current quality levels of chemical, physical and microbiological parameters. Milk delivered weekly or twice weekly to goat cheese manufacturers from 11 farms was sampled over 8 months. Samples were examined for composition, freezing point, extraneous matter, standard plate count, coliforms and inhibitory substances, using Australian Standards Methods. Mean values and (range) for fat, true protein, and lactose were 4.45 percent(2.96 to 5.88); 3.20 percent (2.70 to 4.61); and 4.60 percent' (3.92 to 5.17). Respectively average (range) total solids and ash content were 12.9 percent (11.9 to 15.8); and 1.02 percent (0.69 to 1.53). Freezing points (C) were lower than for cows' milk, viz: - 0.541C (-0.541 to -0.519 C ). Seventy percent of samples had low levels of extraneous matter. Standard Plate Count ranged from 500 cfu/ml to >106/m1 with only 26 percent of samples complying with the standard for cows' milk (5 x 104 cfu/ml). Seventy percent of samples contained coliforms >100 MPN/ml and 30% contained inhibitory substances at levels >0.002 microgram/mI. Setting microbiological standards is premature due to poor over-all quality and an advisory system coupled with quality monitoring is preferred. Standards for other parameters could be set.
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ItemEffects of mulching logging residue on soil water relations, soil temperature and early growth of Pinus radiata on sandy soils in south-west Victoria( 1990)The timber industry in Australia is becoming increasingly dependent on plantations of exotic softwoods, with Pinus radiata D. Don (Monterey pine) the most important species planted in Victoria and South Australia. In general, these plantations have been highly productive in the first rotation. However, in the second rotation there is evidence of a decline in productivity on relatively infertile sandy soils, particularly where the litter and logging residue remaining after clearfelling is burnt. Research has indicated that this decline can be arrested by careful control of cultural inputs, such as chemical weed control, fertiliser and planting of legumes, or by mulching the litter and logging residue. This thesis reports on a study that examined the interacting effects of mulch, weed control and fertiliser on soil and plant water relations, weed biomass, soil temperature, root development, tree growth, and biomass and nutrient accumulation during the first five years following re-establishment of a P. radiata plantation. Mulch, weed control and fertiliser were applied (present, absent) in a 2 x 2 x 2 split-plot factorial design, resulting in eight treatment combinations. Mulch was applied prior to planting; weed control prior to planting and at regular intervals thereafter to age two years; fertiliser at 1.5, 10 and 14 months after planting, a total of 58.1 kg ha-1 of nitrogen and 19.1 kg ha-1 of phosphorus (as part of a complete mineral mix, including zinc). During the first two years after planting, soil and plant moisture levels, soil temperature and tree growth were monitored at four-weekly intervals, and weed biomass three-monthly. Annual growth was also monitored to age five years. Root development, tree biomass and nutrient accumulation were examined in detail at age two years. In the absence of mulch and weed control, soil moisture was significantly reduced during the first two summers after planting due to evapotranspiration losses, with a consequent reduction in tree growth. Both mulch alone and weed control alone were similarly effective in conserving soil moisture in the surface 10 cm of soil, through a reduction in evaporation and transpiration losses respectively. There was evidence that transpiration losses from weeds in mulch had a greater impact than evaporation losses from bare soils at depths from 10 to 40 cm. Maximum soil moisture levels during the summer months occurred where the mulch and weed control treatments were applied together. Mulch reduced weed biomass on average by half for the first two years after planting compared to that on bare soils with no weed control, though weed biomass by mid- to late- summer was similar for both treatments. Weeds which establish in the mulch treatment benefit from improved soil moisture availability as do the P. radiata trees. Mulch significantly reduced soil temperatures compared to those under bare soils during the spring and summer months, particularly in the surface 10 cm of soil. This is likely to have led to less favourable conditions for root growth and mineralisation of soil nitrogen under mulch during spring, when soil moisture availability is not limited by any of the treatments. During summer however, conditions were more favourable under mulch due to higher soil moisture availability. Where mulch and weed control were both applied, root length at age two years was almost twice compared to that for weed control alone. This difference occurred in the surface 10 cm of soil, and is attributed to the combined effect of higher soil moisture availability and stable temperatures within the optimum range for root growth under mulch during the summer months. Roots were also found in the mulch, which indicates that P. radiata roots can either extract nutrients, water or both from the mulch itself. All growth parameters show that in the absence of fertiliser, the responses to mulch alone and weed control alone were similar up to age five years, and that growth was significantly increased when both treatments were applied. These responses were however confounded, as severe zinc deficiency was induced on the weed control alone treatment. In the presence of fertiliser, the responses to mulch alone, weed control alone and both treatments combined were similar by age four years. The largest response to fertiliser was for the weed control alone treatment, probably due to the correction of zinc deficiency. A fertiliser response was initially found where both the mulch and weed control treatments were applied, but by age four years this response was no longer detectable. Growth at age five years was a maximum on, and not significantly different between, the mulch and weed control, mulch and fertiliser, weed control and fertiliser, and mulch, weed control and fertiliser treatment combinations. The nitrogen concentration in needles less than one year-old was at or below the critical level of 14 g kg-1 for all treatment combinations at age two years, except for the weed control alone treatment which was affected by severe zinc deficiency. Despite this, foliage on the treatments associated with good growth did not show obvious nitrogen deficiency symptoms. It is likely that there was net immobilisation of nitrogen under the mulch treatment during the first two years, but subsequent to this it is considered that the mulch would have been a source of nitrogen to the P. radiata trees. Foliar concentrations of both phosphorus and potassium were adequate for all treatment combinations. Foliar concentrations of zinc were at or below the critical level of 10-11 mg kg-1 for those treatments showing maximum growth, which indicates that demands were just being met. They were well below the critical level for the weed control alone treatment. There is clear evidence that the mulched litter and logging residue is a source of zinc to the replanted P. radiata. Relationships between concentration of nutrients in biomass components and tree diameter were generally weak and not significant, and thus nutrient accumulation closely mirrored the pattern of biomass production. The results show that mulching of the litter and logging residue in situ has the beneficial effects of conserving soil moisture, which in combination with more favourable soil temperature conditions during summer, resulted in satisfactory early growth. The results also indicate that mulch is a source of nutrients to the re-established crop. Although care must be taken in extrapolating these results, forest managers should consider mulching as an alternative site preparation technique to burning, particularly on infertile sandy soils.
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ItemDecline of river red gum (Eucalyptus camaldulensis Dehnh.) on grazing lands in Western Victoria( 1988)River Red Gum (Eucalyptus camaldulensis Dehnh.) is a common and extensively distributed tree in western Victoria. Widely-spaced stands of this species are a prominent feature of pastoral landscapes in that area. Many of these remnant stands are in a state of decline, with individuals being lost through deliberate clearing, senescence or the effect of rural dieback disease syndromes. This thesis reports on a study of the decline of one stand of E.camaldulensis trees growing on part of a grazing property near Buangor, in west-central Victoria. The rate of tree loss from agricultural land in the Buangor district was assessed from aerial photographs taken in 1947 and 1980. The average compounding rate of tree loss over that period was 1.1% p.a.. Rates of tree loss were greater from the remnant box-stringybark stands (1.9% p.a.) occurring in the district than from remnant River Red Gum stands (0.8% p.a.). The size and crown condition of all trees in the stand under investigation were assessed. Dieback-affected trees had relatively small and open crowns, that often had many dead branchlets and branches. The crowns of dieback-affected trees were largely of secondary or epicormic origin. Tree height and stem girth were not affected by contemporary crown health. The age of one tree was estimated by radiocarbon dating to be 440. ± 110 y B.P.. Detailed investigations of trees classified as either "healthy", "average" or "unhealthy" were undertaken. The amount of organic matter in soil declined as the quality of tree cover changed from "healthy" to "unhealthy" tree to open pasture. This change was probably linked with reduced additions of organic material through litterfall as tree crown cover deteriorated. The possible consequences of reduced litterfall and declining soil organic matter levels were that; (i) it may have disrupted biogeochemical nutrient cycling; and (ii) it may have increased the susceptibility of trees to root damage and other problems associated with animal traffic. Measurements of soil strength and bulk density indicated that soil under open pasture had been compacted, presumably by animal traffic. Soil under trees was harder during winter than soil under open pasture and was therefore less susceptible to puddling. Soil under trees was not as strong as soil under open pasture during spring and hence provided more favourable conditions for root growth. Investigations into the mineral nutrition of study trees found that "unhealthy" trees did not appear able to mobilize some macronutrient elements (N,P, K, Mg) to the same extent as "healthy" trees. The apparent nutrient deficiency may have been due to disruptions to the biogeochemical nutrient cycle as dieback progressed. The nutrient deficiency may exacerbate this disruption, since it was associated and possibly linked with delayed new foliage production in "unhealthy" trees and reduced area growth in that foliage. Measurements of leaf water potential, diffusive conductance and transpiration showed that atmospheric, rather than soil water deficits had the greatest influence on water relations in the study trees. The measurements showed that "unhealthy" and "average" trees did not greatly restrict transpiration during periods of high evaporative demand. "Healthy" and "average" trees transpired more water and assimilated more carbon than did "unhealthy" trees. Differences in gas exchange were due only to large differences in leaf area. Soil under "healthy" and "average" trees remained drier than soil under "unhealthy" trees and open pasture throughout the study period. However, there was little difference in soil water depletion during the summer, even though the annual pasture had died off. Measurements provide evidence of deep infiltration of water beyond plant root zones, particularly under open pasture and "unhealthy" trees. The healthier trees appeared to have a beneficial impact on the local water balance. Continued rural dieback and/or tree loss is likely to exacerbate disruptions to the local water balance that commenced with clearing for agriculture.
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ItemA study of some aspects of adaptation and yield of Serradella (Ornithopus Spp.) in Victoria( 1989)Serradella (Ornithopus sp.) is potentially useful on deep acid sandy soils in the > 350mm average annual rainfall areas of southern Australia, where many other pasture legumes fail to persist. Subterranean clover (Trifolium sp.) is one of the most important annual pasture legumes usually sown on non-alkaline soils within this climatic region, but it often fails to establish and persist on deep acid sandy soils. In these situations serradella may be a more productive alternative and may become the dominant pasture legume. One of the main limitations to the widespread use of serradella has been the limited amount of genetic variation in Australia, with there being only very few naturalised and commercial strains. In its area of origin, serradella covers the full area of origin of subterranean clover in the Mediterranean region and extends farther into north-western Europe and onto acid sandy soils on which subterranean clover is absent. Yellow serradella (Ornithopus compressus) appears to have the greatest potential for commercial development in Australia, but only one relatively late flowering cultivar, derived from a chance introduction, was available. This was the cultivar Pitman which was suited to an average annual rainfall of 500mm and thus did not leave enough seed for survival of the species in the large areas of grazing land in drier (350-500mm average annual rainfall) areas. In the period from 1970-1980, mainly in an effort to extend the use of serradella to the drier areas, artificially induced mutants of the cultivar Pitman were produced and a wide range of serradella seed was collected from the Mediterranean region. This new variation available to Australian scientists and farmers has been, and is still being, assessed for characters considered to be important for the success of serradella as a pasture legume in Australia. In 1982 seed of 26 of the new accessions, the cultivar Pitman and the Pitman derived mutant, Uniserra, became available to the University of Melbourne for testing under Victorian conditions. These accessions were grown, in single rows and pots, in Gippsland and growth assessments and flowering times were recorded. There was considerable variation in growth response and flowering times and at the end of this trial six lines with good growth were chosen, so that the full range from early to late lines were represented. In the following season, also in Gippsland, the six chosen lines were each sown at five different dates, in single rows with two cultivars of subterranean clover. The flowering and growth responses were recorded allowing direct comparisons to be made. To clarify the comparative vernalization responses of serradella and subterranean clover, a range of accessions of serradella and two cultivars of subterranean clover were grown in the field and in pots in northern Victoria and southern N.S.W., in summer. A similar range of serradella and subterranean clover lines/cultivars was also subjected to artificial vernalization and the resultant flowering responses were recorded. Some of the new accessions flowered earlier than the cultivars Pitman and Uniserra, and the general flowering responses to climate appeared to be similar in both serradella and subterranean clover, with there being similar individual responses between early and late lines of both species. It has been widely reported that on deep acid sandy soils serradella has a more efficient root system, compared with other annual pasture legumes. The cultivar Pitman was grown alongside the subterranean clover cultivar Mt. Barker in an acid sandy loam, treated with varying lime application rates to achieve a range of pH levels (pH 4.3-6.3). The plants were grown in shallow (20cm deep) pots, deep (lm deep) pots and in the field. The application of lime had significant effects on root nodulation, root morphology and root growth of both species. The results generally support the findings of others that serradella's comparative advantage on deep acid sandy soils is due to a finely divided deep root system. A marked feature of serradella appears to be the extensive development of highly branched fine lateral root systems, which can also reach depths of lm.
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ItemEconomic incentives for private softwood plantations in Victoria( 1987)More than 90 per cent of the privately-owned softwood plantations in Victoria are owned by a small number of companies involved in the further processing of softwood timber. This study examines the economic factors influencing the establishment of softwood plantations by other private landholders (i.e. those that do not own softwood processing facilities) and evaluates the economic incentives currently offered to encourage these landholders to establish their own plantations. A number of economic factors contribute to the current low level of planting by private landholders that are not directly involved in the further processing of softwood. These include the structure of the market for softwood in Victoria, the price private growers can expect to receive for their wood, and the long term nature of the investment. The current taxation arrangements for private forestry offer a number of incentives for the establishment of softwood plantations. However they also contain a number of anomalies and disincentives to private forest investment. Various proposals to reform the income tax legislation have been put forward by private grower organizations and by the Commonwealth Government and this study critically evaluates these proposals. The Farm Forestry Agreement Scheme is an incentive scheme that has been offered by the Victorian Government since 1967 to encourage the establishment of private plantations. It offers low-interest loans with repayments deferred for the first 12 years. After more than 15 years operation the total plantings under the Scheme are approximately 8,300 hectares or less than four per cent of the total Victorian softwood resource. Inflation has seriously eroded the incentive value of the Scheme and it is also a very costly and cumbersome scheme to administer. Many Agreement holders are experiencing difficulties in selling wood from their plantations to meet loan repayments and interest in the Scheme has steadily declined in recent years. A number of softwood processing companies operating in Victoria also offer assistance schemes to encourage private landholders to establish their own plantations. The schemes offered by Softwood Holdings Ltd. and APM Forests Ltd. provide private growers with an assured outlet for their timber and have assisted a number of private growers in marketing wood from their plantations. In addition Australian Newsprint Mills Ltd. have recently introduced a scheme known as the Joint Venture Agreement Scheme which offers assistance in the establishment, management and marketing of wood from plantations established jointly by the company and private landholders. The formation of co-operatives of private forest growers offers a number of potential benefits to the owners of private plantations. Of these increased bargaining strength in the marketing of wood and a mechanism for better communication between private growers and softwood processing companies appear to be the most important. The existing incentives and assistance schemes offered by the Government have not been particularly successful in encouraging the establishment of softwood plantations by private landholders. New economic incentives are therefore required if these landholders are to supply an increased proportion of Victoria's future softwood requirements.