School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemMeasurement of the degree of cell rupture in macerated lucerne( 1978)Cell rupture is a critical process in the fractionation of green crops. Despite the importance of this process there is no accepted method for quantitatively describing the degree of cell rupture in a sample of macerated forage. Several methods were investigated and developed as measures of the degree of cell rupture in samples of lucerne leaves macerated by extrusion:- (i) Separation of cells and enumeration of intact cells. (ii) Release of cellular substances:- (a) water soluble carbohydrates (b) potassium (c) sodium (d) electrolytes (e) water (iii) Standard juice expression technique as used by other workers. A total rupture standard was considered to be essential, and was achieved in samples of lucerne leaf tissue macerated initially using a mortar and pestle, followed by ten minutes exposure to ultrasound. The performance of these techniques was evaluated in terms of repeatability and of individual and comparative performance over a large range of degrees of maceration. The cell enumeration method was not developed because a suitable agent for separating the cells of lucerne leaf tissue could not be found. All substance release assays gave repeatable estimates of cell rupture and were highly correlated with each other. It was therefore concluded, that the release of cellular substances gave a reliable estimate of the degree of cell rupture. The standard juice expression technique was insensitive to changes in the degree of rupture and was inaccurate at high levels of rupture. It was concluded that the electrolyte release assay was the most appropriate estimate of cell rupture for use in the future.
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ItemAn evaluation of the role of extension in the Australian pig industry( 1978)Australian agriculture is adjusting to changes in technology, economic circumstances and markets. Extension services as much as the producers' need to change in response to changing industry needs, market trends and consumer demands. There has been much discussion on the problems that these changes present for extension, but none on the basis of empirical research or social science theories. A research program was developed to define the changes taking place in the structure and organisation of the Australian pig industry, and to identify the implications of these changes for pig producers and for extension agencies such as State Departments of Agriculture. The conclusion drawn from the review of the industry situation and from a Delphi survey of 10 experts in the pig industry was that the industry will become more technical and commercialised requiring continual adaptation by the producers to technical and economic changes in order to maintain and increase production efficiency. The survey results showed that a degree of assistance from research and extension was expected by producers to help them maintain and improve production efficiency. Based on the Theory of Personal Constructs, Kelly (1955) an interactive psychological testing procedure known as the Repertory grid was used to record producers' and extension officers' perceptions of each other and of extension services. Twenty pig industry officers, 16 non extension users, 20 extension users and 16 large commercial producers were interviewed. Separate analyses were carried out on the grids of individual subjects, providing profiles of constructs typically used by the subjects in relating to and evaluating people. The results clearly identified the constructs which farmers used in relating to extension advisers and advice. In general, all groups of subjects tended to stereotype people with whom they associated. Combination of both the results within subject groups revealed evidence of commonality within and between the groups in their perceptions. The extension officers saw themselves as progressive and useful while a large number of the producers saw them as theoretical and irrelevant. Extension users held favourable attitudes towards professional agricultural advisers, while large commercial producers and non extension users criticised them on the grounds that they were difficult to communicate with and lacking practical experience. As a group, extension officers were not aware of the questioned relevance of their advice nor of the difficulty experienced by producers in communicating with them. Owing to their practical background and shared experiences, all producers saw other producers as useful and as the most relevant source of advice. The roles they expect him to perform and the characteristics that producers expect from a professional extension adviser have been identified and their implications for the extension officer are discussed. The most obvious implications of the findings are that extension advisers fail to establish the relevance of information within the farmers' context of what is relevant. Based on the findings of the research the theory is proposed that extension programmes will be most successful when producers and extension workers share common perceptions of relevant problems. A philosophy and practice of extension is proposed to meet the farmers' own perception of needs. The interpretation of the results in terms of Personal Construct theory leads to the development of the model of human behaviour, that is, "man as an actor" instead of "man as something being acted upon". A philosophy of extension is developed based on the belief that extension can only be successful if it provides what farmers want. The philosophy states that extension should provide a helping role by facilitating, developing and supporting "man the actor" without dominating or controlling his actions. A practice of extension operating within the boundaries of the proposed new philosophy is developed from the helping relationship model of Carkhuff (1969). The goals of extension are defined as exploration, understanding and action which lead directly to the need for skills which are defined as the "interface skills" of attending, responding, personalising and initiating. The need for and the nature of extension training to provide extension officers with "interface skills" is discussed.
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ItemVegetative and sheep production on a semi-arid Danthonia caespitosa (Gaudich) -Stipa variabilis (Hughes) grassland in response to fertilizers and deferred grazing( 1977)The initial and residual effects of nitrogen and phosphorus fertilizers applied over four consecutive years and gypsum applied once only, were assessed on a Danthonia caespitosa - Stipa variabilis grassland, growing on the semi-arid Riverine Plain of south-eastern Australia. The treatments were combined factorially. The residual effects were assessed over a five-year period from when the fertilizers were last applied. Totals of 155 and 310 kg ha-1 of N, 100 and 200 kg ha-1 of P, and 3.34 and 6.68 tonne ha-1 of CaSO4.2H20 had been added. Seasonal production of total dry matter and individual species, and nitrogen and phosphorus contents of the plant tops, were measured. A simultaneous, but separate, study was made over five years of the effects of nitrogen and phosphorus fertilizers and deferred spring grazing on the bodyweight and wool production of Merino wether weaners grazing a D. caespitosa - S. variabilis grassland at three stocking rates. Seasonal forage availability, botanical composition of forage, bodyweight and wool growth of sheep, were measured. Two years after grazing treatments ceased, and three years after the final addition of fertilizer, further measurements were made on the vegetation. In the first study, during the four years of fertilizer application, forage production increased in response to the additives in years in which the annual rainfall varied from well below to near average. They accentuated the normal pattern of a spring peak, but also gave lesser increases in production in winter and autumn. Summer production was not measured because of the absence of effective summer rainfall. Nitrogen and phosphorus fertilizers and gypsum all contributed to the increased production, and the combination of the three additives produced the greatest yield. Over all seasons the yield of grassland treated with nitrogen plus phosphorus plus gypsum averaged 250 per cent of the control, or approximately 1,500 kg ha-1. The main contributors to increases in yield were D. caespitosa, S. variabilis, annual herbs, and legumes. The perennial grasses were particularly favoured by nitrogen fertilizer whereas the yield of legumes was suppressed. The yield of legumes increased greatly in response to phosphorus fertilizer. With the exception of two species, all plants which increased in yield are acceptable to sheep. Nitrogen and phosphorus contents were above the minimum requirements for domestic herbivores. The study of the residual effects revealed that the increase in dry matter production in response to nitrogen ceased one year after the last application of nitrogen fertilizer. After five years, grassland which had received 200 kg ha-1 of phosphorus and 6.68 tonne ha-1 of gypsum yielded 6,500 kg ha-4 of dry matter, compared with 1,300 kg ha-1 in the absence of fertilizers and gypsum. Legume growth was still suppressed five years after nitrogen fertilizer had been applied, whilst legumes increased production greatly in response to the previous phosphorus and phosphorus-gypsum treatments. Nitrogen content of the herbage averaged 2.1 per cent four years after the previous high level phosphorus treatment, compared to 1.6 per cent with the control after four years. It was unaffected by previous nitrogen fertilizer. Phosphorus content was reduced for the first three years after nitrogen fertilizer was last added, but was increased by phosphorus fertilizer to 0.28 per cent, compared with 0.18 per cent on the control, four years after phosphorus fertilizer was last added. Soil moisture characteristics, and total soil nitrogen and carbon showed no differences between treatments. The Truog phosphorus in the soil under the high phosphorus level decreased from 103 ppm to 53 ppm, compared to the unaltered control level of 7 ppm over the five year period. In the grazing experiment there were very few differences in plant and animal response between the continuously and deferred grazing systems. Forage availability increased on fertilized grassland at all stocking rates by up to 50 per cent. D. caespitosa, S. variabilis, perennial chenopods, and annual herbs contributed to the increase in forage present. Medicago polymorpha became prominent on all fertilized grassland. At 2.0 and 2.7 sheep ha-1 without fertilizer, and 2.7 sheep ha- 1 with fertilizer, the relative contribution by the more palatable species decreased and EriochIamys behrii increased greatly. After grazing treatments ceased, this trend was reversed. Sheep bodyweight and wool growth rates were increased on fertilized grassland. In September 1971, at 2.0 sheep ha-1, the bodyweights of sheep on unfertilized and fertilized grassland were 35.0 and 45.2 kg, respectively, and the clean fleece weights were 3.2 and 4.3 kg per sheep, respectively. Animal production from this grassland can be increased with the addition of fertilizer to the grassland and by increasing the stocking rate by about 50 per cent above the district average of 1.2 sheep per hectare.
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ItemWhole grain for beef cattle( 1979)This thesis consists of a review of feeding processed versus non-processed grain to cattle and reports on several investigations concerned with feeding whole cereal grain to cattle. The experimental section represents a sequence of investigations which attempts to fill information gaps highlighted by the preceding review. They have been prepared as scientific papers and all have been either published or presented for publication. For presentation in this thesis, all have been typed in the one format. I was actively involved in the field work at the Rutherglen Research Station during these investigations, carrying out all of the physical analyses and most of the chemical analyses that were required. I was also responsible for the collation, analysis and interpretation of all the data and the reporting in the scientific papers.
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ItemThe training needs of agribusiness in Australia : a commodity systems approach( 1978)Adopting the concept of agribusiness and the commodity systems approach, this study was conducted to assess the in-service training needs of the human resources in the wheat and the beef commodity systems of Victoria. Having defined the two selected commodity systems in their macro environment, the study concentrated at the level of the individual organization to determine the training needs for the managerial, the professional, and the sales staff. A mail questionnaire survey was conducted with a multi-cluster sampling technique amongst 708 agribusiness organizations in Victoria and a final response rate of 57% was achieved. The findings of this exploratory study indicated: (1) that there were no appreciable differences in the expressed training needs between the two commodities studied (wheat and beef), and amongst the three staff categories (managerial, professional, and sales staff) investigated; (2) that there was a higher level of need for management knowledge rather than for production knowledge; (3) that courses offered by Technical and Tertiary institutions in Victoria in the area of agribusiness were not recipient-oriented, and were seen as unsuitable for their needs; and (4) that the demand for communication training seen in terms of potential staff-numbers was considerable. Some suggestions regarding the implications of these findings have also been made to meet the training needs revealed by the study.
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ItemNitrification and transformations of nitrite in soil nitrogen balance( 1979)Analytical methods were developed to measure nitrogenous gases evolved from soils during nitrification or NO2- transformations. Evolved NO + NO2 is absorbed by an acid solution of potassium permanganate, and the resulting NO3- is determined by a steam distillation procedure. Gas chromatography is used to determine N2 and N20, which are separated on a single column of molecular sieve 5A by temperature programming. Evaluation of closed incubation systems demonstrated that the absorption of NO + NO2 following NO2- addition to a soil, increases with increasing trap : soil surface area and temperature, and decreases with increasing soil water content and depth of soil. Studies of fertilizer N balance and NO2 - transformations required the use of 15N-labelled materials. An apparatus and a procedure were developed to prepare 15N2 for isotope-ratio analysis by mass spectrometry. In laboratory studies, N2, N20 and NO + NO2 were evolved from soils during nitrification of NH3 fertilizer, when soil pH was alkaline. Evidence was obtained to suggest that these losses resulted from chemical reactions involving NO2- . The patterns of gaseous loss in individual soils were very similar to those obtained when NO2- was added to either ?-irradiated or nonirradiated samples. In a calcareous soil, losses were largely prevented by addition of a nitrification inhibitor, which prevented NO2 - accumulation. Nitrite accumulated when pH was alkaline, and NO2 - persistence was related directly to soil pH and inversely to organic C. Gaseous N losses measured in the laboratory did not occur in glasshouse pots treated with 15N-labelled NH3, urea or ammonium sulphate. Possible reasons for this discrepancy are discussed. Studies of the mechanisms of the odenitrification using 15NO2- showed no isotopic dilution of NO + NO2, but N2 was diluted isotopically by approximately 100 percent. It is suggested that NO + NO2 forms through self-decomposition of HNO2, and that N2 may be formed by several mechanisms involving soil organic matter. 15N balance data indicated that another N gas, in addition to N20, was evolved. A significant relationship was demonstrated between the 15N deficit and 15NO2- fixed by soil organic matter. Laboratory incubation and pot experiments demonstrated that NO2- fixed by soil organic matter was resistant to mineralization, but was more readily available than indigenous organic-N. With increasing time, the fixed N becomes more resistant to mineralization. The results of this investigation suggest that champdenitrification may be a mechanism of N loss in fertilizer bands, when Nitrobacter is inhibited. Future avenues of research of the role of nitrification and NO2- transformations in soil nitrogen balance are discussed.
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ItemA study of factors influencing in vitro stability of nitrate reductase from wheat leaves( 1979)This review and the following chapters are concerned predominantly with the processes occurring in higher and lower plants which regulate the amount of NR present in vitro as controlled by degradation, and the level of activity of the existing enzyme. Those factors regulating the synthesis of NR will not be discussed in any detail but only mentioned where they also affect other mechanisms regulating NR. Nitrate reductase is unstable both in vivo and in vitro (101,193, 252). In vitro instability occurs since the isolation of enzymes and other cell components from plant tissue involves disruption of the plant cell. This results in mixing of substances which in situ were rigidly compartmentalized and is likely to result in the isolation of an enzyme which is modified from its native form. Factors present in plant cells which make plant proteins particularly unstable in vitro have been reviewed by Stahrran (216) and Pirie (157). They include vacuole acids, carbohydrates, hydrolytic and oxidative enzymes and phenolic components and their derivatives. In vivo variation in activity occurs in response to a number of other factors, including tissue age (103,129,166,243,264) and environment (15,72,82,1.03,129,261). Tissue age has been shown to influence the activity or stability of NR extracted from a number of species including corn (194,195,264), wheat (221), oats (194,195), tobacco (195) and barley (48). Nitrate reductase has been demonstrated in nearly all plant parts (16) and its ubiquitous presence suggested in higher plants (16,184). Nevertheless, due to the number of factors involved, detection of activity would only occur given suitable physiological and environmental conditions together with use of the correct extraction and assay procedure. Determining if the level of activity derived is an accurate estimate of the in situ activity is even more difficult. This has been attempted by correlating NR activity and grain or plant nitrogen (28, 36) . In vivo instability is indicated by the decline in NR activity with the onset of darkness, depletion of nitrate supply, and water or heat stress (11,82,121,168,235). Under appropriate conditions these factors could also affect the enzyme in vitro.
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ItemMeasuring and improving work performance in milking systems( 1977)Milking represents 40-50% of the total labour input into Australian dairy farms. Unless this work input can be reduced, the job of milking will remain a major limitation to improvements in the efficiency of dairyfarming. The main aim of the field study reported in this thesis was to study the milking and cleaning performance of 15 of the 24 rotary milking systems operating in Australia in the Spring of 1973. Elements of the work routine time were analysed to measure: (a) the relative effects on milking throughput of alternative shed designs, operating systems and types of automation; (b) the relative influence of yard design, shed type, and the operator, on the ease and speed of cow movement from the cowyard onto the rotary platform; and (c) the labour requirements and relative effectiveness of different cleaning systems. Measurements were made at one evening milking and the following morning milking at each farm by 2, 3 or 4 observers, using multi-channel event recorders, stop watches and. recording sheets. Although changes in the element times of the work routine occurred as milking progressed, the labour productivity '(cows milked per man hour) did not change significantly during milking in the group of rotaries studied. Labour productivity was lower at morning milkings than at evening milkings. Productivity increased with increasing number of milking units per operator and, to a lesser extent, with the degree of mechanisation used. The time taken to move cows onto the rotary platforms increased towards the end of milking. The operators increased involvement in cow movement later in milking was partly compensated for by a decrease in his idle time. Operators rated as good, cowmen spent less time encouraging, forcing or assisting cows onto the platform than those operators rated as below average cowmen. Cows defecated less on "turnstyle" type rotary platforms than on rotary herringbone platforms which had no provision for head yoking of the cows. Although there were no significant differences in "cow-in" times or percentage of cows needing assistance onto the platform between circular and rectangular type holding yards, cow behaviour was slightly better in the group of rectangular yards studied. Mechanisation substantially reduced the amount of time spent on cleaning milking machines. It is clear that all milking systems have considerable potential for mechanisation. The amount and type of labour saved must establish the priorities put on mechanising the' various tasks involved in milking and cleaning. Mechanisation of the milking routine is pointless unless there is a corresponding increase in the number of milking units per operator. Techniques for data collection and presentation must be simplified and standardised to enable comparison of results between surveys and between milking systems, e.g. throughput should be expressed as cows per man hour per milking unit as well as cows per man hour, to permit meaningful comparisons. Good cowmanship is critical to the success of a milking system. "Cowmanship" needs to be clearly defined and. further investigated. Variations in milker and cow behaviour in the milking systems studied in the survey indicate that the principle of shifting the emphasis from one of forcing cows to conform, to one of encouraging them to ca-operate by conditioning and training, warrants further research
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ItemThe effect of applied N and P under mowing and grazing on the yield and botanical and chemical composition of irrigated pasture and on the nutrient status of a red-brown earth at Kyabram( 1978)A split plot experiment was conducted over 4 years to study the effect of method of harvesting (grazing and mowing) and applied N and P (5 rates of nitrogen ranged from 0 to 112 kg N ha -1 cut-1 and 6 rates of superphosphate ranged from 0 to 188 kg P ha 1 year year-1) on the yield, botanical and chemical composition of irrigated phalaris (Phalaris tuberosa x Phalaris arundinacea)/white clover (Trifolium repens L. cv. Irrigation) pasture and nutrient status of a red-brown earth at Kyabram. A second experiment was conducted over 2 years to find out the effect of rates (0 to 112 kg N ha. 1) and frequency of N application (2, 4 or 8 times year ) o n dry matter production, botanical composition and crude protein content of paspalum (Paspalum dilatatum)/white clover pasture. Results: Mowed plots significantly out-yielded grazed plots in the first two years. However, grazed plots significantly out-yielded mowed plots in the following two years. Nitrogen application significantly (P <0.01) increased dry matter production of grass/clover mixtures. The size of response was governed by the growth rate of pasture species, clover percentage in the sward, climatic conditions and the status of other nutrients in the soil. Splitting N rates in smaller but more frequent applications had no effect on total herbage yield or seasonal distribution. Response to N (kg D.M. kg N-1 ) declined as N rates increased. Phosphorus application up to 94 kg P ha -1 year -1 significantly (P,(0.01) increased pasture production and relative response was greater in winter. Occasionally, the P and N requirements for maximum production were higher for grazing than for mowing. Both methods of defoliation and fertilizer applications affected pasture composition and IT, P and K content in the herbage. Nitrogen application decreased N in the herbage before increasing it and P application up to 141 kg P ha- 1 year -1 increased it. The return by the grazing animal increased total soil N by 106 kg ha 1 year 1 and soil P (Colwell) by 1:0 p.p.m. in four years compared with the start of the experiment. The relationship between plant P and soil P and P rates were significant (P < 0.01). The available soil P decreased with P withdrawal or the application of 23.5 kg P ha-1 year -1 under grazing and 47 kg P ha -1 year-1 under mowing. Phosphorus and nitrogen application significantly affected available soil P. 60-80% of the available P accuminulated in the 0-5 cm and the downward movement increased by increasing P rates. The continuous mowing and P application significantly reduced available soil K. Defoliation method affected C/t:N ratio. Phosphorus application increased soil N whereas N application decreased it. P application at the rate of 23.5 kg ha-1 year-1 increased total soil N by 0.068% which is equivalent to 952 kg N ha-1 in five years. It was estimated that 4 to 4.7 p.p.m of P was required to be removed or added to the soil to change the available soil P by 1 p.p.m. The application of 196 kg N ha-1 year -1 as NH4 NO3 did not change the soil pH and 784 kg N ha 1 year 1 reduced soil pH by an average of ').4 unit.
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