School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemMaking the connection between history, agricultural diversity and place: the story of Victorian apples( 2016)Apple growing practices are embedded in a productivist mentality aiming for ever higher efficiency and productivity. And while the climate change impacts are to a large extent known, there is little attention given to the coupling of the social and the ecological effects. I use apple growing as a case study to explore the relationship between place, biodiversity and rural change in Victoria. My research is based on historical research; including an analysis of the Museum Victoria’s collection of wax apple models, and in-depth interviews with orchardists. By drawing on environmental history, social-ecological systems thinking and Bourdieu's theory of practice, I highlight the importance of a systems perspective and inform it by emphasis on the critical role of underlying power structures and individual dispositions, or the habitus, of the growers. These dispositions have been shaped and internalised by the growers’ histories and their physical surroundings. Orchardists have been able to respond to intensifying production requirements by utilizing technologies and scientific nous to keep up with the continuous aim for efficiency. Growers are caught up in a self-reinforcing cycle of satisfying the demand for perfect apples by adopting expensive techno-scientific approaches to enable ever more intensive production. The symbolic violence and amplified biophysical pressure orchardists experience has driven many to despair; resulting in a significant decline in small scale apple growing businesses over the last decade. I offer some suggestions for government policy and support measures and argue that any services or support programs need to be tailored to the appropriate level and need of each orchard business and the individuals who are involved. My analysis shows that those growers, who engage more closely with their biophysical place as well as their history and identity as apple growers in that place are (re-)creating another version of what it means to be an apple grower. In some cases this is resulting in resistance to the vortex of agricultural productivism that has been the basis of their existence for many generations.
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ItemStudies of Ascochyta rabiei in Australia( 2005)Ascochyta rabiei (teleomorph: Didymella rabiei) which causes ascochyta blight is the most serious disease of chickpea (Cicer arietinum) in Australia as it causes significant losses in crop yield and quality. Although A. rabiei is heterothallic and genetically diverse elsewhere in the world, a study carried out on Australian isolates collected between 1995 and 2000 identified only one mating type and a low level of genetic diversity within the Australian A. rabiei population. In 2002, ascospores of Didymella rabiei, the sexual state of A. rabiei, were trapped in a discharge chamber, from chickpea stubble naturally infected with ascochyta blight in Western Australia. Examination of the stubble revealed pseudothecia typical of Didymella rabiei. The reported presence of the teleomorph in Western Australia indicated that the second mating type had been introduced into Australia or that the pathogen was capable of a low level of homothallic compatibility, previously undetected. The aims of this research were, to undertake a new survey of Australian A. rabiei isolates, to test for the presence of the second mating type, to determine if there has been a change in the diversity of the Australian population and to investigate if pathogenic variability was displayed among isolates. Sixty-seven isolates collected from chickpea fields in South Australia, New South Wales, Queensland, Victoria and Western Australia during the 2003 cropping season were single spored and confirmed as A. rabiei using a PCR test. The isolates were typed for mating type using MAT gene specific PCR primers and compared with tester isolates from USA. This test revealed that all the 67 isolates belonged to mating type 2 (MAT 1-2), thus, the presence of mating type 1 (MAT 1-1) in Australia could not be confirmed. Sequence Tagged Micro Satellite (STMS) markers were used to examine the genetic diversity of the A. rabiei isolates. The isolates were assessed for allelic variation at 19 microsatellite loci, each of which amplified a single locus. Seven of the loci were polymorphic across all the 67 isolates, while the remaining twelve were monomorphic. Based on the allele profiles at the seven polymorphic loci, 19 distinct A. rabiei haplotypes were identified with a total of 33 alleles. One haplotype constituted 35.8 % of the population and was found in the collections from South Australia, New South Wales, Queensland and Victoria. Cluster analysis did not show a clear distinction between isolates based on the state from which they were collected. Polymorphism across the 19 microsatellite loci revealed a slight elevation in diversity in the 2003-2004 population (Ht = 0.07; compared to 0.02 in the 1995 to 2000 collection) and an increase in the number of haplotypes compared with that detected in the previous study of Australian isolates. To examine the pathogenic variability of the Australian population of A. rabiei, nine isolates were inoculated on five chickpea differentials, ranging from highly susceptible to resistant, under controlled conditions optimal for A. rabiei growth and infection. Eight of the isolates were virulent on the susceptible and intermediate chickpea cultivars but not the resistant cultivar and one isolate was only virulent on the susceptible cultivar. Based on these results the isolates were classified into two pathotype groups. The results obtained from the study of the population structure and the pathogenic variability of A. rabiei in Australia will enable the Australian chickpea breeders to understand the A. rabiei population better for formulating management and breeding strategies.
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ItemEffects of adding nutrients on soil chemistry and tree growth in native Eucalyptus forests of south-eastern Australia( 2007)The decreasing area available for timber extraction in south-eastern Australia, due largely to social pressure to reserve greater areas of forest, has led to the consideration of fertiliser-application to increase wood output from the remaining available forest. Potentially deleterious effects of fertilising on water quality must be assessed before implementation on a wide scale. This is in accordance with relevant forest management policies. This study examined the effects of applying fertilisers containing nitrogen and phosphorus, on soil and soil-water chemistry in two pole-sized stands of mixed Eucalyptus spp in the Wombat Forest, in the Midlands Forest Management Area, Victoria, Australia. The findings are synthesised and discussed in relation to management of regenerating mixed-eucalypt forests in south-eastern Australia. Fertiliser treatments were none (R); 400 kg N ha-1 as ammonium-sulphate (N); or 400 kg ha-1 plus 202 kg P ha-1 as triple superphosphate coated with 10% sulphur (NP). It was calculated that incidental additions of S were 1371 kg ha -1 (N treatments), and 1696 kg ha-1 (NP treatments). It was expected that P would be principally adsorbed on soil surfaces; N immobilised in the soil organic pool and that metallic cations would enter the soil solution to varying degrees. Fertiliser-addition increased both plot-basal-area (BA) growth and the rate of stand self-thinning. In 3.8 years, BA in reference (R) plots at two sites increased by 7.3% and 23.4%. Where N alone was added, BA increased by 14.2% and 27.1%, while in NP plots BA increased by 17.1% and 42.7% respectively. Mortality was 9% in untreated plots compared to 14% in NP plots. Estimated increases in biomass growth equated to additional above-ground nutrient accumulation of 0.4 to 1.5 kg ha-1 of P, and 5.5 to 20.8 kg ha-1 of N. This represented only 0.2 to 0.7% of added P, and 1.4 to 5.2% of added N. Soil solution was extracted from 10 and 50 cm with porous-ceramic-cup tension-lysimeters (-0.6 kPa). Concentrations of P and N were low both before and after adding fertiliser. Across all treatments the maximum median PO43- concentration in soil-water at 50 cm was 0.12 ppm (mean 0.28 ppm). Typically PO43- concentrations were not higher than 0.03 ppm. The 400 kg ha-1 of added N was rapidly immobilised in the soil organic pool. The greatest mean NH4' concentration from a single sampling occasion was 1.1 ppm. The mean NO3 concentration at 50 cm was never higher than 0.26 ppm. After adding N in fertiliser the proportion of NO3- relative to NH4* in soil-water increased and was correlated with decreasing soil-water pH. Less than 1% of added P and N was recovered from soil solution at 50 cm. The largest pool of added P recovered was PO43- adsorbed to soil between 0 and 20 cm, due to the soil adsorption capacity being well in excess of the applied 202 kg P ha-1. Phosphate desorption using sequential extractions with a mild acid extractant (0.3M NH4F, 0.1M HCI) recovered between 25% and 116% of added P. Differences were attributed to both the amount of P added and the effect of time since treatment at different sites. Soil disturbance during sampler installation was found to be more likely to raise soil-water P concentrations at 50 cm than would adding up to 202 kg P ha-1. Among the ions in solution. SO42- and CI' were the dominant anions while Cat+ dominated the cation chemistry. In untreated forest 5042- in soil-water ranged from 7.7 to 16.0 ppm at 10 cm and 7.9 to 12.2 ppm at 50 cm. In fertilised plots up to 100.5 ppm SO42 was measured in soil-water at 50 cm depth. In the N treatment at 50 cm, SO42- in soil-water accounted for 9.4 % of applied S. compared to 14.0 % in NP. In untreated forest, soil-water Cl- and SO42- accounted for over 98% of the total soil-water anions, in roughly equal proportions at 10 cm, and CI- slightly higher at 50 cm. Following fertiliser-application soil-water pH at 10 cm fell from 6.3 in R to as low as 4.81 (N) and 4.45 (NP). At 50 cm pH never dropped below 6 and there were no visible departures from reference concentrations. Relative activities of K+ and Mg2+ in solution increased with decreasing pH, indicating increased leaching potential. Sulphate in soil-water increased total anion charge further in NP than in N. Total charge (cmolc L-1) for cations followed anions. A slight deficit in anion charge was likely due to the unquantified contribution of organic anions. These results confirm that despite the quantity of fertilisers added in this trial being double likely operational quantities, the forest and associated soils had the capacity to retain these nutrients through a variety of processes. The study validates the environmental sustainability of proposed intensive management practices including fertiliser-application in this forest type. It also emphasises the importance of understanding fundamental forest nutrient cycling processes when aiming to carry out intensive forest management practices in an environmentally sensitive manner.
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ItemEffects of organic applicants in a southern Victorian vineyard( 2007)Mulch is a material applied to the surface of the soil to reduce weed growth and reduce soil moisture loss through evaporation from the soil surface. The use of organic mulches will alter the soil environment. This alteration may include reducing soil temperature fluctuations, increasing soil organic matter, increasing soil microflora populations modifying soil chemical properties and increasing soil moisture retention. An experiment was conducted to compare composted green waste mulch and barley straw mulch with herbicide as alternative means of maintaining the undervine strip in a cool climate vineyard. Plant and soil responses to the different undervine treatments were monitored. Grapevine budburst was retarded, however, by the fourth week of vine growth there were no observable differences in grapevine growth stage. Both mulches stimulated grapevine growth and increased yield, with the compost mulch increasing vegetative growth with respect to fruit yield. The fruit quality parameters juice pH and titratable acidity were not significantly altered by the different undervine treatments. In the second year of the experiment the juice soluble solids were lower on the straw mulched grapevines. The compost mulch increased soil pH and carbon levels. The straw mulch improved soil water retention and the mass of soil fungal hyphae. Both mulches increased soil cation exchange capacity. The straw mulch increased soil exchangeable Mg to a greater extent than was predicted from straw nutrient content. The significant variations seen in soil cation content under the mulch treatments were not observed in the tissue analysis. Mulch can be used in a cool climate vineyard to increased yield without deleterious side effects.
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ItemRural credit and farm viability : a study of the Shelford soldier settlement scheme( 1973)The accelerated fall in wool prices towards the end of the 1960's precipitated the emergence of a financial crisis in the sheep industry with high farm debts and low farm incomes. The subject of rural credit, which had provoked only minor discussion throughout the buoyant income periods of the 1950's and 1960's, became increasingly debated by farm leaders who challenged the suitability of the existing credit market to meet the increasing capital needs of the rural sector. Since the implementation of the rural reconstruction scheme in 1971 which provides assistance for a limited number of unviable farmers, farmer demands for more general concessional credit facilities have intensified. Recently, following submissions by several farmer organizations to the Government for assistance, the subject of rural credit has rapidly developed into a political issue. This thesis is a study of farm indebtedness and the rural credit market in a woolgrowing community of soldier settlers in the Leigh Shire of the Victorian Western District. The area was chosen because it was thought that the settlers, hard hit by the 1967-68 drought, and heavily dependent on the profitability of woolgrowing, would be suffering severe financial problems. The economic analysis was restricted by the lack of suitable empirical data. The original survey data, collected by the Agricultural Extension Section of the University by personal interviews with farmers, did not include farm costs or inventory levels. Because this was a pilot study, the data was cross-sectional, referring only to the survey year. Before proceeding with the analysis, it was necessary to obtain additional financial information from the taxation records of co-operating farmers. The thesis was written before but submitted after the release of a Bureau of Agricultural Economics report (B.A.E. 1972) advising the Government on the adequacy of existing credit facilities. Consequently, no reference has been made elsewhere in the thesis to this report. The thesis is organized as follows. Chapters 1 and 2 provide a general introduction to farmers' borrowing behaviour, the existing rural credit market, and the debt position of the rural sector, especially the sheep industry. In chapter 3, the Shelford settlement is discussed with emphasis on the debt position of Shelford farmers and their use of credit facilities. In chapter 4, an attempt is made to relate the financial position of farmers to their physical resource levels and social characteristics. The variance in debt and income are analysed. Chapter 5 contains a discussion of some past influences on the current debt position, especially the 1967-68 drought. In chapter 6, the present and future prospects of farm financial viability are studied. Some commonly used indicators of viability are evaluated within the Shelford context. The dependence of settlers on short term lenders and the future role these lenders are likely to play at Shelford and elsewhere are discussed in chapter 7. Finally in chapter 8, the role of credit in agricultural adjustment is discussed. A solution for unviable Shelford farmers is proposed and some brief comments on the shortcomings of the present credit market are advanced. Conclusions are presented throughout the thesis, and chapter 7 and 8 form a summary of the rural credit situation in general and at Shelford.
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ItemA systems analysis approach to drought reserves in the Hamilton region( 1971)Following a discussion of drought strategies available to the grazier, one particular strategy, the holding of drought fodder reserves, is examined in detail. The study estimates the least-cost fodder reserves for a range of stocking rate-pasture production regimes in the Hamilton region. The amount of hay feeding required on any stocking-pasture regime is determined from a simulation model of the grazing complex. In this model, three levels of pasture production are stocked at rates ranging from one to ten wethers per acre. The pasture production assumed ranges from "excellent" (i.e. equivalent to the Hamilton Research Station pastures which produce about 10,000 lb. dry matter per annum) to "poor" (35% less). The climatic inputs into the grazing model are the date of Autumn break, for which a formula is derived, and the June to October rainfall. The pasture sub-model is specified and used to derive the pasture which is "grown" in the grazing model. The sheep aspects of the model are reviewed in detail to derive the relationships which are used in the next set of four sub-models in which animal intake is simulated and liveweight changes determined. This set of four sub-models provides for the four situations of animal intake which may be met. These are: The intake of green pasture alone (i.e. all pasture grown after the Autumn Break); the intake of hay alone; the intake of hay and green pasture together; the intake of hay and dry pasture (pasture remaining when the Autumn Break occurs and dry pasture alone which are handled in the same sub-model) The grazing model was validated for the years 1965-67 using data from the Pastoral Research Station, Hamilton, and showed good agreement for all three years simulated, one of which featured a severe drought. Drought feeding requirements (hay) are determined for each of the years 1879 to 1967 and for the ten stocking rate-pasture production regimes, using specific hay feeding rules. These rules, which aim at sheep survival, do not attempt to specify optimum feeding rates per sheep, and any change in them could significantly alter the drought requirements for any of the regimes studied. Furthermore, the estimates are Lased on the assumption that all sheep are fed through the drought. A pre-drought strategy which permitted the sale of certain classes of sheep at some stage during drought would entail lower feed requirements and might have a lower expected cost, especially at high acquisition costs for feed and low replacement costs for sheep. An inventory analysis is then undertaken, based on a 12 month planning period, which utilises the hay feeding probabilities generated in the grazing model, and provides estimates of the least-cost hay reserve. In contrast to previous studies, the price of hay is related to drought length in calculating the penalty cost of inadequate reserves. The effects of varying several parameters of the inventory model are then examined. The parameters varied are hay costs ($4, $10 and $16 per ton), interest rates (7%, 20% and 50%), and salvage values, and these vary in association with the parameters varied in the grazing model (stocking rate, pasture production and the area closed for hay). At the intermediate values for pasture production and hay cost and a 7 per cent per annum interest rate, the minimum-cost reserve rises sharply, from 2 bales per acre at 2 wethers per acre, to 4.5 bales per acre at 3 wethers per acre, 8 bales per acre at 4 wethers per acre, and 15 bales per acre at 5 wethers per acre. The minimum-cost reserve was found to be relatively insensitive to changes in acquisition costs, except at low stocking rates, where a change in reserve of one or two half-bales per sheep was common as acquisition cost varied over the three levels. The effect of interest rates was also examined for the average pasture regime. On the lowest level of hay acquisition cost, ($4 per ton) increasing the rate of interest from 7 to 50 per cent caused reductions of only one half-bale per sheep. However, at high acqusition cost ($16 per ton) raising the interest rate to 20 per cent resulted in a considerable reduction in the minimum-cost reserve, especially on the lower stocking rates, and raising the interest rate to 50 per cent made holding fodder reserves uneconomic for any stocking rate. One measure of the risk in holding various levels of fodder reserve is the standard deviation of the total expected cost. As expected, it was found that this declines as the reserve is expanded to the maximum ever required. However, only a small reduction in standard deviation results from expanding the reserve beyond the minimum-cost level. Finally, estimates were made of the income-maximising stocking rate for each level of pasture production and hay cost, with the wool price at 30, 40 and 50 cents per lb.. At the intermediate values for pasture production (8,000 lb. D.M.) and hay cost ($10 per ton), and with wool at 30 cents per lb. net, the income-maximising stocking rate was 3 wethers per acre. Each increase of 10 cents per lb. in the wool price was generally associated with an increase of one or two wethers per acre in the income-maximising stocking rate. An increase of 2,000 lb. D.M. (from "average" to "excellent") in average annual pasture production was generally associated with an increase of one wether per acre in the income-maximising stocking rate. A reduction of 1,500 lb. from "average" to "poor" pasture. production reduced the income-maximising stocking rate by about one wether per acre. Increasing the hay cost from $4 to $10 per ton reduced the profit-maximising stocking rate by one wether per acre for all combinations of pasture production and wool price examined. However, a further increase in acquisition cost from $10 to $16 per ton only caused a further reduction in the income-maximising stocking rate at the poor level of pasture production: with average pasture production there was little change and with excellent production there was no change in the income-maximising stocking rate.