School of Agriculture, Food and Ecosystem Sciences - Theses

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Economic evaluation of feeding grain to dairy cows in Western Victoria

Kelly, Hugh D. (University of Melbourne, 1999)

This study is set in Western Victoria, where the dairy farming systems are characterized by springdominant pasture growth, low pasture growth in summer and moderate growth of pasture in autumn. This, coupled with either late winter calving or early autumn calving, creates pasture deficits, which occur in early and late lactation. The challenge for farmers in Western Victoria is to fill those feed gaps with supplements with the aim of maintaining or increasing profitability. Over a production year, feed supply is provided by a mix of fixed and variable inputs. Variable inputs such as working capital, fertilizers, seed, rainfall, irrigation, conserved fodders and concentrate feeds are added to the land, cows, labour and capital infrastructure. The worth of any one of these variable inputs is determined by the amount it contributes to the farm profitability during the production year. The aim of this study is to evaluate the economic effects of different grain feeding regimes on dairy farms in Western Victoria and determine whether net benefits could be gained from implementing a range of possible grain feeding regimes. Pasture based animal production systems are complicated because of the way the animals, water, pasture, fodder and concentrates interact during different stages of the production year. This means that both a short and medium term view has to be taken to make decisions about feed supply. There is also a need to evaluate the effect of unexpected changes to variable input supply and contingency measures that can be adopted to minimise negative impacts on the system. Further complications arise when trying to evaluate the changes to dairy farming systems because the production response function of each cow and the herd cannot be exactly known with great accuracy before the feed decisions are taken. As well, the law of diminishing marginal returns is at work all the time. The research undertaken in this project was based on a series of case studies of dairy farms in different areas throughout Western Victoria. These farms were selected to represent the different types of farming systems and areas within the region. The operation of the farms was studied at considerable depth to gain a thorough understanding of how each farming system operated. The operation of the farm was modeled using the dairy farm simulation program called UDDER, which can be used to simulate water-animal-pasture- fodder-concentrate interactions for different types of feeding strategies. Their effects on milk production over a year can be evaluated. A series of changes to the grain feeding regime were simulated on each farm to evaluate whether gains could be achieved from altering the timing and quantity of grain fed during the year. The technical information from the model UDDER was then analysed in an economic context using a partial budget model that was developed. This partial budget decision support tool helps farmers identify the essential feeding factors that affect the viability of a farming system and the relative merit of alternative grain feeding tactics and strategies. In this project it was identified that net gains could be made with strategic increases in grain feeding on the individual farming systems. Generally, if the grain fed to the dairy herd was increased during early and late lactation, extra gains were predicted to be achievable. However, substantial gains were also predicted if extra grain was fed to the herd during mid-lactation. When grain feeding levels were reduced, large losses were experienced. This indicates the reliance of the case study dairy herds on grain to produce milk if they are to maintain their current levels of profitability. This study shows that farmers may be able to earn larger profits with greater precision in quantity and timing of grain feeding. However, increases in some grain feeding will not always provide immediate extra gains. Like farm management in general, dairy feed management involves finding and mastering the key pieces of information and processing it in the whole farm context with both tactical and strategic perspectives in mind.
Economic evaluation of feeding grain to dairy cows in Western Victoria

Kelly, Hugh D. (University of Melbourne, 1999)

This study is set in Western Victoria, where the dairy farming systems are characterized by springdominant pasture growth, low pasture growth in summer and moderate growth of pasture in autumn. This, coupled with either late winter calving or early autumn calving, creates pasture deficits, which occur in early and late lactation. The challenge for farmers in Western Victoria is to fill those feed gaps with supplements with the aim of maintaining or increasing profitability. Over a production year, feed supply is provided by a mix of fixed and variable inputs. Variable inputs such as working capital, fertilizers, seed, rainfall, irrigation, conserved fodders and concentrate feeds are added to the land, cows, labour and capital infrastructure. The worth of any one of these variable inputs is determined by the amount it contributes to the farm profitability during the production year. The aim of this study is to evaluate the economic effects of different grain feeding regimes on dairy farms in Western Victoria and determine whether net benefits could be gained from implementing a range of possible grain feeding regimes. Pasture based animal production systems are complicated because of the way the animals, water, pasture, fodder and concentrates interact during different stages of the production year. This means that both a short and medium term view has to be taken to make decisions about feed supply. There is also a need to evaluate the effect of unexpected changes to variable input supply and contingency measures that can be adopted to minimise negative impacts on the system. Further complications arise when trying to evaluate the changes to dairy farming systems because the production response function of each cow and the herd cannot be exactly known with great accuracy before the feed decisions are taken. As well, the law of diminishing marginal returns is at work all the time. The research undertaken in this project was based on a series of case studies of dairy farms in different areas throughout Western Victoria. These farms were selected to represent the different types of farming systems and areas within the region. The operation of the farms was studied at considerable depth to gain a thorough understanding of how each farming system operated. The operation of the farm was modeled using the dairy farm simulation program called UDDER, which can be used to simulate water-animal-pasture- fodder-concentrate interactions for different types of feeding strategies. Their effects on milk production over a year can be evaluated. A series of changes to the grain feeding regime were simulated on each farm to evaluate whether gains could be achieved from altering the timing and quantity of grain fed during the year. The technical information from the model UDDER was then analysed in an economic context using a partial budget model that was developed. This partial budget decision support tool helps farmers identify the essential feeding factors that affect the viability of a farming system and the relative merit of alternative grain feeding tactics and strategies. In this project it was identified that net gains could be made with strategic increases in grain feeding on the individual farming systems. Generally, if the grain fed to the dairy herd was increased during early and late lactation, extra gains were predicted to be achievable. However, substantial gains were also predicted if extra grain was fed to the herd during mid-lactation. When grain feeding levels were reduced, large losses were experienced. This indicates the reliance of the case study dairy herds on grain to produce milk if they are to maintain their current levels of profitability. This study shows that farmers may be able to earn larger profits with greater precision in quantity and timing of grain feeding. However, increases in some grain feeding will not always provide immediate extra gains. Like farm management in general, dairy feed management involves finding and mastering the key pieces of information and processing it in the whole farm context with both tactical and strategic perspectives in mind.
Fallow-crop water balance and recharge relationships in the Victorian Mallee

O'Connell, M. G. (Mark Glenn) (University of Melbourne, 1998)

Background: The Victorian Mallee has a semi-arid climate and cereal production is the major agricultural landuse. Alkaline calcareous soils dominate the region. Cropping in the Mallee is subject to variation in growing season rainfall. Long (winter) fallows are a robust and common practice prior to wheat. Fallows may be viewed as a drought prevention strategy in the rainfed Mallee. Water conserved by fallows supplements growing-season rainfall and thereby reduces annual yield variability. The risk is wind erosion and deep drainage beyond the rootzone of crops. Deep drainage represents incomplete utilisation of water for crop production and contributes to dryland salinity when it enters saline groundwater (potential groundwater recharge) (Chapter 1). This thesis presents work conducted in the field by experimentation and by simulation modelling. A field study at Walpeup (35� 07' S., 141� 58' E.) was conducted over 5 years (1993-1997) to investigate substituting mustard (Brassica juncea) for 18-month long-fallows. Two crop sequences (fallow-wheat-pea [FWP] v. mustard-wheat-pea [MWP]) were examined. The field experiments were designed to appraise FWP v. MWP sequences by investigating soil-water balance, productivity, potential recharge to groundwater and episodic drainage (Chapters 2 & 3). Determination of crop interception and utilisation of photosynthetically active radiation (PAR) were investigated in the field (Chapter 4). Simulation modelling was used to identify cropping practices conducive to longterm productivity and minimal drainage in the region. The O'Leary-Connor model (O'Leary and Connor 1996a,b) was appraised against observed measures (1993- 1998) of growth and yield of wheat, and rootzone soil-water balance under wheat and fallow (Chapter 5: Experiment I). Effects of crop rotation, stubble and tillage management on deep drainage of light (sandy loam) and heavy (clay) textured soils were then investigated by running the O'Leary-Connor model using 58 y of historical climatic data (Chapter 5: Experiment II). Field experimentation: The field experiment demonstrated effects of substituting mustard for fallowing. Aspects of water balance, growth and yield of FWP and MWP sequences were investigated in Chapter 2. Water limited crop production in each growing-season throughout the study. Rootzone soil-water conservation from fallowing in sequence FWP increased wheat growth, yield and water use under severe drought. By contrast, the data reveal that pea water relations and productivity was not influenced by crop sequence. Mustard growth was variable with low yields. Deep drainage was investigated (1993-1998) under FWP and MWP sequences by measuring changes in subsoil-water and by drainage lysimetry (Chapter 3). The former showed greater drainage of FWP (12 mm/y) compared to MWP (5 mm/y). Two major drainage events were confined to a specific phase of the FWP sequence (5.0 mm & 4.3 mm), illustrating the difficulty of reconciling drainage estimates by alternative approaches in a semi-arid environment over a relatively short period 5 y). Radiation interception by wheat, pea and mustard was investigated in Chapter 4. The fraction of intercepted PAR (f), canopy extinction coefficient and radiation-use efficiency were determined for each crop. Aridity resulted in incomplete canopy cover. Fallowing increased f of wheat under favourable (1996) and drought (1994) growing seasons. Estimates of extinction coefficient for wheat, pea and mustard were 0.82, 0.76 and 0.68, respectively. Estimated pre-anthesis radiation-use efficiency for wheat, pea and mustard were 1.75, 1.47 and 1.85 (g aboveground biomass/MJ intercepted PAR), respectively. Simulation modelling: The O'Leary-Connor model provided a good representation of wheat growth, and rootzone soil water (Chapter' 5: Experiment I), justifying use of the unadjusted model, as a tool for examination of water balance under agronomic scenarios in this study (Chapter 5: Experiment II). The investigation suggested greater soil-water conservation under fallowing compared to continuous cropping. Simulated grain yield responded to trends in soil water in accordance with water limitations imposed by the rainfed environment. Simulated drainage was episodic. Soil hydraulic properties and agronomic management influenced total drainage. Least drainage occurred on the heavy textured clay, reflecting soil-water holding capacity and water use associated with crop production. No direct relationships between drainage and rainfall were evident. Continuously cropped (WW) sequences drained less than fallow-wheat (FW). Fallow management influenced water storage and drainage. Stubble-retained zerotilled fallows conserved more soil water and subsequently had greatest drainage. Conventional tillage and stubble burning decreased drainage, but increased runoff and soil surface evaporation. On the lighter soil type, WW and FW drained ~6 % of years without stubble retention, but 10-70 % of years when stubble was retained, with a increase in drainage from 0.5 mm/y to 10-20 mm/y, respectively. By contrast, the heavier clay failed to drain without stubble, and drained in the range, 5-24 % of years when stubble was retained (range, 2-17 mm/y). Overall, fallowing reduced yield failure, but, in conjunction with stubble retention, increased episodic and total drainage on both soil types under the climatic conditions experienced in the Mallee. Conclusion: Outcomes of both field and simulation studies confirms that fallowing increases drainage (potential groundwater recharge). Although, non-fallow annual cropping sequences failed to provide a dry soil profile at sowing for prevention of drainage, especially in wet years. Strategies that use agronomic perennials to dewater subsoils prior to sowing require further investigation.
Fallow-crop water balance and recharge relationships in the Victorian Mallee

O'Connell, M. G. (Mark Glenn) (University of Melbourne, 1998)

Background: The Victorian Mallee has a semi-arid climate and cereal production is the major agricultural landuse. Alkaline calcareous soils dominate the region. Cropping in the Mallee is subject to variation in growing season rainfall. Long (winter) fallows are a robust and common practice prior to wheat. Fallows may be viewed as a drought prevention strategy in the rainfed Mallee. Water conserved by fallows supplements growing-season rainfall and thereby reduces annual yield variability. The risk is wind erosion and deep drainage beyond the rootzone of crops. Deep drainage represents incomplete utilisation of water for crop production and contributes to dryland salinity when it enters saline groundwater (potential groundwater recharge) (Chapter 1). This thesis presents work conducted in the field by experimentation and by simulation modelling. A field study at Walpeup (35� 07' S., 141� 58' E.) was conducted over 5 years (1993-1997) to investigate substituting mustard (Brassica juncea) for 18-month long-fallows. Two crop sequences (fallow-wheat-pea [FWP] v. mustard-wheat-pea [MWP]) were examined. The field experiments were designed to appraise FWP v. MWP sequences by investigating soil-water balance, productivity, potential recharge to groundwater and episodic drainage (Chapters 2 & 3). Determination of crop interception and utilisation of photosynthetically active radiation (PAR) were investigated in the field (Chapter 4). Simulation modelling was used to identify cropping practices conducive to longterm productivity and minimal drainage in the region. The O'Leary-Connor model (O'Leary and Connor 1996a,b) was appraised against observed measures (1993- 1998) of growth and yield of wheat, and rootzone soil-water balance under wheat and fallow (Chapter 5: Experiment I). Effects of crop rotation, stubble and tillage management on deep drainage of light (sandy loam) and heavy (clay) textured soils were then investigated by running the O'Leary-Connor model using 58 y of historical climatic data (Chapter 5: Experiment II). Field experimentation: The field experiment demonstrated effects of substituting mustard for fallowing. Aspects of water balance, growth and yield of FWP and MWP sequences were investigated in Chapter 2. Water limited crop production in each growing-season throughout the study. Rootzone soil-water conservation from fallowing in sequence FWP increased wheat growth, yield and water use under severe drought. By contrast, the data reveal that pea water relations and productivity was not influenced by crop sequence. Mustard growth was variable with low yields. Deep drainage was investigated (1993-1998) under FWP and MWP sequences by measuring changes in subsoil-water and by drainage lysimetry (Chapter 3). The former showed greater drainage of FWP (12 mm/y) compared to MWP (5 mm/y). Two major drainage events were confined to a specific phase of the FWP sequence (5.0 mm & 4.3 mm), illustrating the difficulty of reconciling drainage estimates by alternative approaches in a semi-arid environment over a relatively short period 5 y). Radiation interception by wheat, pea and mustard was investigated in Chapter 4. The fraction of intercepted PAR (f), canopy extinction coefficient and radiation-use efficiency were determined for each crop. Aridity resulted in incomplete canopy cover. Fallowing increased f of wheat under favourable (1996) and drought (1994) growing seasons. Estimates of extinction coefficient for wheat, pea and mustard were 0.82, 0.76 and 0.68, respectively. Estimated pre-anthesis radiation-use efficiency for wheat, pea and mustard were 1.75, 1.47 and 1.85 (g aboveground biomass/MJ intercepted PAR), respectively. Simulation modelling: The O'Leary-Connor model provided a good representation of wheat growth, and rootzone soil water (Chapter' 5: Experiment I), justifying use of the unadjusted model, as a tool for examination of water balance under agronomic scenarios in this study (Chapter 5: Experiment II). The investigation suggested greater soil-water conservation under fallowing compared to continuous cropping. Simulated grain yield responded to trends in soil water in accordance with water limitations imposed by the rainfed environment. Simulated drainage was episodic. Soil hydraulic properties and agronomic management influenced total drainage. Least drainage occurred on the heavy textured clay, reflecting soil-water holding capacity and water use associated with crop production. No direct relationships between drainage and rainfall were evident. Continuously cropped (WW) sequences drained less than fallow-wheat (FW). Fallow management influenced water storage and drainage. Stubble-retained zerotilled fallows conserved more soil water and subsequently had greatest drainage. Conventional tillage and stubble burning decreased drainage, but increased runoff and soil surface evaporation. On the lighter soil type, WW and FW drained ~6 % of years without stubble retention, but 10-70 % of years when stubble was retained, with a increase in drainage from 0.5 mm/y to 10-20 mm/y, respectively. By contrast, the heavier clay failed to drain without stubble, and drained in the range, 5-24 % of years when stubble was retained (range, 2-17 mm/y). Overall, fallowing reduced yield failure, but, in conjunction with stubble retention, increased episodic and total drainage on both soil types under the climatic conditions experienced in the Mallee. Conclusion: Outcomes of both field and simulation studies confirms that fallowing increases drainage (potential groundwater recharge). Although, non-fallow annual cropping sequences failed to provide a dry soil profile at sowing for prevention of drainage, especially in wet years. Strategies that use agronomic perennials to dewater subsoils prior to sowing require further investigation.
Innovation in response to environmental problems

Ewers, Craig. (University of Melbourne, 1990)

An important and long-standing field of agricultural extension research has involved the acceptance of new agricultural practices. Consistent with the applied, purposive nature of extension research and the emphasis on agricultural development, this field has centred around the question: How do we get farmers to adopt new technology? As such, the process has traditionally been viewed as one which is confined to the decisions of individual farmers. The role of those who develop and distribute the technology has generally been overlooked. It is argued in this thesis that when the development and promotion of agricultural technology are an integral part of government strategy, a great deal of decision-making happens before the technology even reaches the farm. Indeed, it will be shown that some innovations developed by government scientists may not become fully available to farmers. The complex interplay between science, technology and government policy forms a central theme throughout this thesis. Changes in agricultural practice are discussed with reference to the social and economic conditions that triggered them. In particular, the growing impact of the environmental movement on the development and diffusion of new cropping techniques throughout the 1980s is covered in depth. Two current Victorian government programs are critically reviewed along these lines. Finally, the views of farmers are analysed, through a survey of 146 wheat growers in North-East Victoria.
Innovation in response to environmental problems

Ewers, Craig. (University of Melbourne, 1990)

An important and long-standing field of agricultural extension research has involved the acceptance of new agricultural practices. Consistent with the applied, purposive nature of extension research and the emphasis on agricultural development, this field has centred around the question: How do we get farmers to adopt new technology? As such, the process has traditionally been viewed as one which is confined to the decisions of individual farmers. The role of those who develop and distribute the technology has generally been overlooked. It is argued in this thesis that when the development and promotion of agricultural technology are an integral part of government strategy, a great deal of decision-making happens before the technology even reaches the farm. Indeed, it will be shown that some innovations developed by government scientists may not become fully available to farmers. The complex interplay between science, technology and government policy forms a central theme throughout this thesis. Changes in agricultural practice are discussed with reference to the social and economic conditions that triggered them. In particular, the growing impact of the environmental movement on the development and diffusion of new cropping techniques throughout the 1980s is covered in depth. Two current Victorian government programs are critically reviewed along these lines. Finally, the views of farmers are analysed, through a survey of 146 wheat growers in North-East Victoria.
Control of the black field cricket teleogryllus commodus (walker) (orthoptera: gryllidae) in Victoria

Murphy, Graeme, 1954- (University of Melbourne, 1985)

Techniques for improving control of the black field cricket Teleogryllus commodus were studied between 1981 and 1985 in series of laboratory and field trials in the western district of Victoria. In the laboratory, techniques were developed for assessing the palatability of substances to T. commodus. A number of plant extracts, especially water and acetone extracts from grasses, and other substances including sucrose and vegetable oils were shown to stimulate feeding in the cricket. Further laboratory trials showed that feeding stimulants could be used to encourage feeding on a commonly used substrate in cricket baits (wheat). Field trials to assess bait attractiveness revealed oats to be more attractive as a bait than wheat or barley. Efficacy trials conducted over consecutive years however, showed no differences in the level of control achieved with baits using wheat, oats or barley as the substrate. In addition, feeding stimulants added to the bait did not improve control, nor did the use of higher baiting rates. The level of control obtainable with the current recommended bait is between 80% and 95%.
Aspects of the biology and salt tolerance of Phragmites australis (Cav.) Trin. ex Steud.

Clucas, Rowena D. (University of Melbourne, 1980)

Reeds thrive under a wide range of conditions, but in the Gippsland Lakes system, high salinity levels - both alone and in conjunction with other environmental factors - have greatly reduced Phragmites growth on the shoreline and removed the reed fringe entirely in some areas. The Gippsland Lakes system provides an unstable environment, where salinity levels and water levels fluctuate seasonally and also between drought and flood years. Distribution of reeds along the lake edges is correlated primarily with salinity levels, but also with exposure to wind, wave and current action. The amount of salt absorbed by reeds is directly related to site salinity. High salinities reduce many aspects of productivity, including shoot height, density and dry weight, and seed production. The actual salinity tolerance of Phragmites in the field is dependent upon the severity and duration of the salinity regime and other habitat factors operating. Conditions on the north shore of Lake Wellington are near the tolerance limit of Phragmites. Reeds accumulate large quantities of mineral elements and growth is greatly improved in areas of high nutrient status. Phragmites can readily be grown from rhizome or shoot cuttings if these are collected at the appropriate stage of development. Establishment from seed is a rare occurrence in the field and germination depends on the formation of viable fruits. In the three Victorian populations studied, less than two per cent of the florets contained viable seed.
Adoption of agronomic technologies by farmers

Konstantinidis, Jim ( 1999)
The effect of oxygen and carbon dioxide atmospheres on the quality of packaged fresh-cut lettuce

G�zukara, Yesim Meltem ( 1999)

The present study investigated the potential of using alternative storage atmospheres to maintain microbial and storage quality of fresh-cut lettuce salad mix for longer periods than those currently obtained in air and traditional low oxygen (O2): high carbon dioxide (CO2) modified atmosphere packaging (MAP). The outcome of this research was to assist the freshcut industry through improved shelf life and safe food supply. The effects of modified atmospheres containing air or 100% oxygen at pH 5.0, 6.0 and 7.0, on the growth and survival of two strains of Pseudomonas fluorescens (FSAW 3107 and ATCC 13525) were determined on an agar surface at 5C for 10 days. The aim of this preliminary study was to determine the response of this spoilage organism in a model system where the surfaces of packaged chilled fresh-cut vegetable and MAP conditions were simulated. The results demonstrated the ability of two different strains of Ps. fluorescens to survive and grow in storage atmospheres of up to 100% O2 tested at any of the pH levels, except pH 5.0. The reduction in the pH of the medium to 5.0 was sufficient to inhibit the growth of the bacteria regardless of storage atmospheres. Further studies compared the impact of 100% O2, 80% O2 : 20% CO2, passive MAP and air atmospheres on the microbial growth and storage quality of fresh-cut lettuce mix stored at 5C for 10 days, using four packaging films of differing gas permeabilities. The study also compared and evaluated the suitability of barrier, experimental, and commercial packaging films for using the 80% O2 : 20% CO2 gas mixture. A 100% O2 storage atmosphere maintained with the barrier packaging film inhibited enzymatic browning in lettuce tissue, as determined by visual assessment and colour measurements. On visual examination, the product was still acceptable for consumption after 10 days of storage at 5C, compared to all other film and atmosphere treatments. Polyphenol oxidase activity declined in lettuce stored under 80% O2 : 20% CO2 and passive MAP storage atmospheres, and was the lowest at 100% O2 treatment compared with that of air, and the atmosphere conditions that developed where high permeability experimental films were used. Accumulation of CO2 to levels above 20% in the barrier and commercial packaging films initially flushed with 80% 02 : 20% CO2 gas composition resulted in several disorders in lettuce, such as severe tissue softening and development of off-odours. The same gas mixture used with a high permeability experimental film stabilised at 20.0% O2 and 5.2 % CO2, and the product quality was poorer than in all other treatments except for lettuce stored under air. Fresh-cut lettuce stored in commercial MAP bags had a passively modified atmosphere comprising 0.9% O2 : 17.1% CO2 after 10 days at 5C. The quality of this product was not acceptable after 8 days, due to discolouration of lettuce and off-odours. In conclusion, of the modified atmospheres tested, 100% O2 retained an acceptable visual quality of fresh-cut lettuce salad mix at 5C, without a marked effect on the growth of pseudomonads, Enterobacteriaceae and the total viable count. The choice of film permeability was also demonstrated to be an important factor when using the alternative storage atmospheres. Film permeabilities that would allow development of storage atmospheres containing CO2 above 20% with high oxygen levels, should not be used since this was shown to promote physiological damage of the fresh-cut lettuce.

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