School of Agriculture, Food and Ecosystem Sciences - Theses

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Salinity control, water reform and structural adjustment : the Tragowel Plains Irrigation District

Barr, Neil F. (University of Melbourne, 1999)
Epidemiology of mint rust and variation in the Pathogen, Puccinia menthae Pers

Edwards, Jacqueline. (University of Melbourne, 1998)
Genetics of resistance to Heterodera avenae in Triticum tauschii and its transfer to bread wheat (Triticum aestivum)

Eastwood, Russell Francis. (University of Melbourne, 1995)
A decision support system for sustainable forest management

Varma, Vivek Krishna (University of Melbourne, 2000)

The main objective of this study is to develop a decision support system for sustainable forest management that employs criteria and indicators; preferably one that enables the process to be adaptive over successive cycles of monitoring indicators, thereby capitalizing to the fullest on the criteria and indicators approach. To meet this objective, this thesis develops (1) a methodology for monitoring indicators over time, and (2) a procedure appropriate for achieving a sustainable forest resource allocation, based on a review of literature. The resulting decision support system blends the decision maker's knowledge with the information processing capabilities of the computing tools employed and is applicable on the regional scale. The application of potentially useful criteria and indicators framework faces considerable difficulties due to: the issues of integration of spatial and non-spatial data coming from a variety of sources; the choice of methodologies to analyse the large quantities of data; the incorporation of joint production characteristics of forest values; the lack of reliable and cost-effective data, and; the uncertainty associated with data, sustainability thresholds, and decision-rules. The proposed monitoring methodology addresses these issues. It comprises uncertainty-based multi-criteria evaluation of the indicators at a forest management unit level using a geographic information system. It also focuses on determining two alternative indices of sustainability. These indices are calculated by using Zadeh's fuzzy set theory and Dempster-Shafer theory of evidence to model the uncertainty in sustainability thresholds and decision-rule respectively. They proved to be similar in nature. This monitoring methodology was applied to Landsat 5 TM data for the East Gippsland Region, Australia, with the objective of examining the design of the land-use indicators over successive monitoring cycles. While confirming the usefulness of the satellite imagery as a source of data on large spatial scales, this study highlighted the importance of classification errors in reliably monitoring indicators over short periods. A case study on Aravalli Project, India, was developed to demonstrate utility of the monitoring methodology by applying a range of indicators, including some specially framed area-specific indicators, to participatory forest management. The results of both studies emphasised the need of reliable `ground-truth' data for implementing criteria and indicator framework. The approach developed for sustainable forest resource allocation and land-use planning potentially provides a basis for ensuring a `non-declining total utility' accruing from the diverse forest values to the current and future generations. It satisfactorily addresses, in a utilitarian framework, several important issues, such as incorporating social preferences while satisfying intra- and intergenerational equity concerns; efficiency; complexity; uncertainty, and ecological irreversibility. Stochastic and fuzzy/ possibilistic approaches were used to deal with uncertainty on the short and long planning horizons respectively in a linear programming model that employed the concept of aspiration levels. A heuristic procedure was developed to distribute land units spatially to various forest values. Implementation of this approach required the integration of a geographic information system, mathematical modelling software, simulation models, graphic user interfaces, specially written computer programmes, and database management system. This decision support system, based on an ethically-oriented approach, could facilitate a more informed, and probably more socially and politically acceptable, public decision-making for achieving sustainability of forest resources.
A decision support system for sustainable forest management

Varma, Vivek Krishna (University of Melbourne, 2000)

The main objective of this study is to develop a decision support system for sustainable forest management that employs criteria and indicators; preferably one that enables the process to be adaptive over successive cycles of monitoring indicators, thereby capitalizing to the fullest on the criteria and indicators approach. To meet this objective, this thesis develops (1) a methodology for monitoring indicators over time, and (2) a procedure appropriate for achieving a sustainable forest resource allocation, based on a review of literature. The resulting decision support system blends the decision maker's knowledge with the information processing capabilities of the computing tools employed and is applicable on the regional scale. The application of potentially useful criteria and indicators framework faces considerable difficulties due to: the issues of integration of spatial and non-spatial data coming from a variety of sources; the choice of methodologies to analyse the large quantities of data; the incorporation of joint production characteristics of forest values; the lack of reliable and cost-effective data, and; the uncertainty associated with data, sustainability thresholds, and decision-rules. The proposed monitoring methodology addresses these issues. It comprises uncertainty-based multi-criteria evaluation of the indicators at a forest management unit level using a geographic information system. It also focuses on determining two alternative indices of sustainability. These indices are calculated by using Zadeh's fuzzy set theory and Dempster-Shafer theory of evidence to model the uncertainty in sustainability thresholds and decision-rule respectively. They proved to be similar in nature. This monitoring methodology was applied to Landsat 5 TM data for the East Gippsland Region, Australia, with the objective of examining the design of the land-use indicators over successive monitoring cycles. While confirming the usefulness of the satellite imagery as a source of data on large spatial scales, this study highlighted the importance of classification errors in reliably monitoring indicators over short periods. A case study on Aravalli Project, India, was developed to demonstrate utility of the monitoring methodology by applying a range of indicators, including some specially framed area-specific indicators, to participatory forest management. The results of both studies emphasised the need of reliable `ground-truth' data for implementing criteria and indicator framework. The approach developed for sustainable forest resource allocation and land-use planning potentially provides a basis for ensuring a `non-declining total utility' accruing from the diverse forest values to the current and future generations. It satisfactorily addresses, in a utilitarian framework, several important issues, such as incorporating social preferences while satisfying intra- and intergenerational equity concerns; efficiency; complexity; uncertainty, and ecological irreversibility. Stochastic and fuzzy/ possibilistic approaches were used to deal with uncertainty on the short and long planning horizons respectively in a linear programming model that employed the concept of aspiration levels. A heuristic procedure was developed to distribute land units spatially to various forest values. Implementation of this approach required the integration of a geographic information system, mathematical modelling software, simulation models, graphic user interfaces, specially written computer programmes, and database management system. This decision support system, based on an ethically-oriented approach, could facilitate a more informed, and probably more socially and politically acceptable, public decision-making for achieving sustainability of forest resources.
Studies on resynchronisation of oestrus with progesterone and oestradiol benzoate in Holstein cows

Eagles, Vicki Maree. (University of Melbourne, 2000)

Resynchronisation of return-to-service in cows using progesterone and oestradiol benzoate is an integral part of current recommendations for Controlled Breeding Programs and the treatment of postpartum anovulatory anoestrus to improve herd reproductive performance. This thesis describes the results of a series of three experiments designed to test some of the hypotheses on the principles of resynchronisation based on each of the following questions: a) What concentrations of plasma progesterone are sustained by re-using a CIDR device for resynchronisation as compared to concentrations sustained by a new device? b) What proportion of the cows that are not confirmed pregnant to first insemination can be successfully resynchronised; and, do any pregnant cows show overt symptoms of oestrus as a consequence of the resynchronisation treatment? c) Does the type of the resynchronisation treatment for cows originally diagnosed with anovulatory anoestrus affect the efficacy of treating this common condition in Holstein cows? Experiment 1: To identify changes in plasma progesterone concentration, a sequence of treatments with a new or recycled CIDR device in ovariectomised cows was used to model the respective plasma progesterone profiles in treated cycling or anoestrous cows. A total of 9 ovariectomised non-lactating Holstein cows were each treated sequentially with a new CIDR device inserted for 6 days (Round 1); then a new CIDR device was inserted 4 days after the first device was withdrawn, with an insertion period of 6 days (Round 2); and finally, the same device initially used in Round 1 was re-inserted for a period of 7 days (Round 3). A 1mg oestradiol benzoate injection was administered 24 hours after device removal at the conclusion of each Round. Every cow was observed for signs of behavioural oestrus during the subsequent 72 h period. Blood samples were taken at specified intervals during the period of device insertion (3 hours, Day 1 and Day 6 post-insertion), as well as immediately preceding device insertion and following removal 6 or 7 days later. The average plasma progesterone concentrations over the 6-day insertion period for each Round 1, 2 and 3 were: 3.2, 2.2 and 1.7 ng/mL, respectively. Concentrations were significantly higher in Round 1 (P<0.01), but were similar in Rounds 2 and 3. The highest progesterone concentrations in Round 1 were those measured 3 and 24 hours after device insertion. This reflected the delay in the induction of hepatic enzymes that metabolise progesterone and are not normally required by ovariectomised cows. The progesterone content of a CIDR device declined by 23% (1.83g 1.41g) over the first 6 days of insertion and by a further 20% (1.41g -� 0.98g) over the second 7 days of insertion. Every cow displayed obvious overt symptoms of behavioural oestrus within 48 hours of being injected with oestradiol benzoate in each Round. In conclusion, ovariectomised cows were a suitable model to characterise subtle changes in the concentration of plasma progesterone which occurred in response to administration of a new or recycled CIDR device per vaginum for 6 or 7 days. The profile of changes in plasma progesterone as a consequence of device insertion and removal was rapid and was influenced by previous exposure to progesterone. Similar plasma progesterone profiles were associated with the use of a new CIDR device or a recycled device when animals had been previously exposed to elevated levels of progesterone. Experiment 2: The characterisation of the profile of changes in plasma progesterone concentration in response to a resynchronisation treatment initiated during middioestrus and subsequent to a synchronised first oestrus, in lactating Holstein cows involved in a commercial Controlled Breeding Program. It was also to determine if a recycled device could elevate plasma progesterone concentration to delay the onset of oestrus and synchronise returns-to-service. Plasma progesterone concentrations were measured before, during and following the resynchronisation treatment with a recycled CIDR device. Every enrolled cow (n=42) which had been initially synchronised using progesterone, prostaglandin F2a and oestradiol benzoate along with about 160 herd mates, had a recycled CIDR device re-inserted per vaginum 13 days after its first insemination. Most (n=30) of these cows were also injected with 1mg oestradiol benzoate (Group 2 & Group 3) at device re-insertion and every one of them was injected with the same dose of oestradiol benzoate 24 hours after device removal occurring 7 (Group 2) or 8 (Group 1 & Group 3) days after re-insertion. These variations in resynchronisation treatment did not affect any of the measured responses. There were two distinct populations of progesterone concentrations based on 4 blood samples taken 24 hours following device removal. The High progesterone sub-group (n=23) averaged 4.15 ng/mL (range=1.42 to 6.77 ng/mL); the Low progesterone sub-group (n= 19) averaged 0.08 ng/ml (range 0.03 to 0.14 ng/mL). Every one of the latter sub-group was detected in oestrus and inseminated from 24 to 96 hours after device removal. None of the animals in the former subgroup was detected in oestrus. However, 4 of these 23 animals (17%) were subsequently found to have not established a normal pregnancy, even though they had progesterone concentrations at 26 days after their first insemination which were indistinguishable from their 19 contemporaries who were confirmed pregnant to first insemination. These 4 cows were typical of those described as "Phantom Cows." In conclusion, resynchronisation treatment with a recycled device was effective in extending the oestrous cycle and stimulated return-to-service of animals with low plasma progesterone concentrations during the expected period of return within 96 hours after device removal. The treatment was less efficient at synchronising oestrus in animals which were retrospectively diagnosed not pregnant at pregnancy diagnosis 6 to 8 weeks after the conclusion of the Al period ("Phantom Cow Syndrome") but which had high plasma progesterone concentrations throughout the resynchronisation period. Experiment 3: To evaluate the reproductive responses of varied resynchronisation methods initiated during mid-dioestrus (Day 13 post-insemination) with progesterone and oestradiol benzoate to synchronise returns-to-service in cows which had initially received a standard treatment for anovulatory anoestrus; and to demonstrate the reproductive impact on the 6-week in-calf rate of these cows compared to their untreated cycling herd mates. A total of 810 cows which were diagnosed as anoestrus in 16 seasonally calving (3556 total cows) herds serviced by the Maffra Veterinary Clinic in 1998 were initially treated with progesterone by inserting a CIDR device for 6 days, and then injecting oestradiol benzoate (1mg) at 24 hours after device removal. Within 72 hours of this injection, 691 of these cows (85.3%) were detected in oestrus and inseminated. Each of these 691 cows had a recycled CIDR device re-inserted 16 days after initial device removal (13 � 1 day post-first insemination) and was also injected with 1mg oestradiol benzoate. The re-inserted device was withdrawn after 7 days. On the eighth day, half of these cows (n=334) were injected with 0.5mg oestradiol benzoate (2 x ODB; Group 2) while the other half (n=357) received no further treatment (1 x ODB; Group 1). a) The improved reproductive performance of cows in Group 2 occurred because more cows returned for a second insemination over the 4-day period following the second oestradiol benzoate injection (post-device removal) (44.6% versus 28.3%); b) the re-submission rate among cows subsequently confirmed as not conceiving to first insemination was greater (65.3% versus 40.1%); c) and the conception rates to first or second inseminations were similar for cows in the two Groups (1St = 29% versus. 32%; 2nd = 44.5% versus. 46.4%). The pregnancy rate for cows in Group 2 increased from 33.4% on Day 22 of inseminating to 55.4% by Day 26 compared to changes from 31.9% to 48.7% for cows in Group 1. The median interval from mating start date to conception for cows in the Group 2 was 23 days compared to 42 days for cows in Group 1 and 25 days for cycling herd mates. Comparable mean intervals to conception for these Groups were 31.2, 34.0 and 27.8 days respectively. Final in-calf figures for those animals in Group 2 were similar to those for cycling cows (86.5% versus. 85.4%), and higher than those for cows in Group 1 (82.9%; P<0.05). The results of this trial showed that the form of resynchronisation treatment had a significant effect on the outcome and the efficacy of treating cows for anovulatory anoestrus. In summary, this series of trials showed that: a) recycled CIDR devices released sufficient progesterone to resynchronise oestrus in previously synchronised cows; b) the resynchronisation treatments used in a Controlled Breeding Program achieved the desired objective among cows in which luteolysis had occurred spontaneously during the period of re-treatment without producing a false oestrus in cows with high plasma progesterone concentrations following resynchronisation; c) the resynchronisation treatment used in cows with anovulatory anoestrous requires oestradiol benzoate (0.5mg) to be injected after device removal to increase submission rates to the second insemination; and, d) that the resynchronisation treatment was ineffective with "Phantom Cows" Further studies are still required for improvement to be gained in the fertility of the first oestrus following hormonal treatment and the subsequent resynchronised inseminations of treated anovulatory anoestrous cows to achieve similar reproductive performance to their untreated cycling herd mates. In addition, a better understanding of the characteristics of the "Phantom Cow" following a first insemination is required to develop both management strategies and effective hormonal therapy to reduce their impact on herd fertility. These two factors combined are major limitations resulting in compromised reproductive performance in lactating Holstein cows in the commercial seasonally calving herds in Victoria.
Studies on resynchronisation of oestrus with progesterone and oestradiol benzoate in Holstein cows

Eagles, Vicki Maree. (University of Melbourne, 2000)

Resynchronisation of return-to-service in cows using progesterone and oestradiol benzoate is an integral part of current recommendations for Controlled Breeding Programs and the treatment of postpartum anovulatory anoestrus to improve herd reproductive performance. This thesis describes the results of a series of three experiments designed to test some of the hypotheses on the principles of resynchronisation based on each of the following questions: a) What concentrations of plasma progesterone are sustained by re-using a CIDR device for resynchronisation as compared to concentrations sustained by a new device? b) What proportion of the cows that are not confirmed pregnant to first insemination can be successfully resynchronised; and, do any pregnant cows show overt symptoms of oestrus as a consequence of the resynchronisation treatment? c) Does the type of the resynchronisation treatment for cows originally diagnosed with anovulatory anoestrus affect the efficacy of treating this common condition in Holstein cows? Experiment 1: To identify changes in plasma progesterone concentration, a sequence of treatments with a new or recycled CIDR device in ovariectomised cows was used to model the respective plasma progesterone profiles in treated cycling or anoestrous cows. A total of 9 ovariectomised non-lactating Holstein cows were each treated sequentially with a new CIDR device inserted for 6 days (Round 1); then a new CIDR device was inserted 4 days after the first device was withdrawn, with an insertion period of 6 days (Round 2); and finally, the same device initially used in Round 1 was re-inserted for a period of 7 days (Round 3). A 1mg oestradiol benzoate injection was administered 24 hours after device removal at the conclusion of each Round. Every cow was observed for signs of behavioural oestrus during the subsequent 72 h period. Blood samples were taken at specified intervals during the period of device insertion (3 hours, Day 1 and Day 6 post-insertion), as well as immediately preceding device insertion and following removal 6 or 7 days later. The average plasma progesterone concentrations over the 6-day insertion period for each Round 1, 2 and 3 were: 3.2, 2.2 and 1.7 ng/mL, respectively. Concentrations were significantly higher in Round 1 (P<0.01), but were similar in Rounds 2 and 3. The highest progesterone concentrations in Round 1 were those measured 3 and 24 hours after device insertion. This reflected the delay in the induction of hepatic enzymes that metabolise progesterone and are not normally required by ovariectomised cows. The progesterone content of a CIDR device declined by 23% (1.83g 1.41g) over the first 6 days of insertion and by a further 20% (1.41g -� 0.98g) over the second 7 days of insertion. Every cow displayed obvious overt symptoms of behavioural oestrus within 48 hours of being injected with oestradiol benzoate in each Round. In conclusion, ovariectomised cows were a suitable model to characterise subtle changes in the concentration of plasma progesterone which occurred in response to administration of a new or recycled CIDR device per vaginum for 6 or 7 days. The profile of changes in plasma progesterone as a consequence of device insertion and removal was rapid and was influenced by previous exposure to progesterone. Similar plasma progesterone profiles were associated with the use of a new CIDR device or a recycled device when animals had been previously exposed to elevated levels of progesterone. Experiment 2: The characterisation of the profile of changes in plasma progesterone concentration in response to a resynchronisation treatment initiated during middioestrus and subsequent to a synchronised first oestrus, in lactating Holstein cows involved in a commercial Controlled Breeding Program. It was also to determine if a recycled device could elevate plasma progesterone concentration to delay the onset of oestrus and synchronise returns-to-service. Plasma progesterone concentrations were measured before, during and following the resynchronisation treatment with a recycled CIDR device. Every enrolled cow (n=42) which had been initially synchronised using progesterone, prostaglandin F2a and oestradiol benzoate along with about 160 herd mates, had a recycled CIDR device re-inserted per vaginum 13 days after its first insemination. Most (n=30) of these cows were also injected with 1mg oestradiol benzoate (Group 2 & Group 3) at device re-insertion and every one of them was injected with the same dose of oestradiol benzoate 24 hours after device removal occurring 7 (Group 2) or 8 (Group 1 & Group 3) days after re-insertion. These variations in resynchronisation treatment did not affect any of the measured responses. There were two distinct populations of progesterone concentrations based on 4 blood samples taken 24 hours following device removal. The High progesterone sub-group (n=23) averaged 4.15 ng/mL (range=1.42 to 6.77 ng/mL); the Low progesterone sub-group (n= 19) averaged 0.08 ng/ml (range 0.03 to 0.14 ng/mL). Every one of the latter sub-group was detected in oestrus and inseminated from 24 to 96 hours after device removal. None of the animals in the former subgroup was detected in oestrus. However, 4 of these 23 animals (17%) were subsequently found to have not established a normal pregnancy, even though they had progesterone concentrations at 26 days after their first insemination which were indistinguishable from their 19 contemporaries who were confirmed pregnant to first insemination. These 4 cows were typical of those described as "Phantom Cows." In conclusion, resynchronisation treatment with a recycled device was effective in extending the oestrous cycle and stimulated return-to-service of animals with low plasma progesterone concentrations during the expected period of return within 96 hours after device removal. The treatment was less efficient at synchronising oestrus in animals which were retrospectively diagnosed not pregnant at pregnancy diagnosis 6 to 8 weeks after the conclusion of the Al period ("Phantom Cow Syndrome") but which had high plasma progesterone concentrations throughout the resynchronisation period. Experiment 3: To evaluate the reproductive responses of varied resynchronisation methods initiated during mid-dioestrus (Day 13 post-insemination) with progesterone and oestradiol benzoate to synchronise returns-to-service in cows which had initially received a standard treatment for anovulatory anoestrus; and to demonstrate the reproductive impact on the 6-week in-calf rate of these cows compared to their untreated cycling herd mates. A total of 810 cows which were diagnosed as anoestrus in 16 seasonally calving (3556 total cows) herds serviced by the Maffra Veterinary Clinic in 1998 were initially treated with progesterone by inserting a CIDR device for 6 days, and then injecting oestradiol benzoate (1mg) at 24 hours after device removal. Within 72 hours of this injection, 691 of these cows (85.3%) were detected in oestrus and inseminated. Each of these 691 cows had a recycled CIDR device re-inserted 16 days after initial device removal (13 � 1 day post-first insemination) and was also injected with 1mg oestradiol benzoate. The re-inserted device was withdrawn after 7 days. On the eighth day, half of these cows (n=334) were injected with 0.5mg oestradiol benzoate (2 x ODB; Group 2) while the other half (n=357) received no further treatment (1 x ODB; Group 1). a) The improved reproductive performance of cows in Group 2 occurred because more cows returned for a second insemination over the 4-day period following the second oestradiol benzoate injection (post-device removal) (44.6% versus 28.3%); b) the re-submission rate among cows subsequently confirmed as not conceiving to first insemination was greater (65.3% versus 40.1%); c) and the conception rates to first or second inseminations were similar for cows in the two Groups (1St = 29% versus. 32%; 2nd = 44.5% versus. 46.4%). The pregnancy rate for cows in Group 2 increased from 33.4% on Day 22 of inseminating to 55.4% by Day 26 compared to changes from 31.9% to 48.7% for cows in Group 1. The median interval from mating start date to conception for cows in the Group 2 was 23 days compared to 42 days for cows in Group 1 and 25 days for cycling herd mates. Comparable mean intervals to conception for these Groups were 31.2, 34.0 and 27.8 days respectively. Final in-calf figures for those animals in Group 2 were similar to those for cycling cows (86.5% versus. 85.4%), and higher than those for cows in Group 1 (82.9%; P<0.05). The results of this trial showed that the form of resynchronisation treatment had a significant effect on the outcome and the efficacy of treating cows for anovulatory anoestrus. In summary, this series of trials showed that: a) recycled CIDR devices released sufficient progesterone to resynchronise oestrus in previously synchronised cows; b) the resynchronisation treatments used in a Controlled Breeding Program achieved the desired objective among cows in which luteolysis had occurred spontaneously during the period of re-treatment without producing a false oestrus in cows with high plasma progesterone concentrations following resynchronisation; c) the resynchronisation treatment used in cows with anovulatory anoestrous requires oestradiol benzoate (0.5mg) to be injected after device removal to increase submission rates to the second insemination; and, d) that the resynchronisation treatment was ineffective with "Phantom Cows" Further studies are still required for improvement to be gained in the fertility of the first oestrus following hormonal treatment and the subsequent resynchronised inseminations of treated anovulatory anoestrous cows to achieve similar reproductive performance to their untreated cycling herd mates. In addition, a better understanding of the characteristics of the "Phantom Cow" following a first insemination is required to develop both management strategies and effective hormonal therapy to reduce their impact on herd fertility. These two factors combined are major limitations resulting in compromised reproductive performance in lactating Holstein cows in the commercial seasonally calving herds in Victoria.
Nitrogen dynamics after application of biosolids to a Pinus radiata plantation

Robinson, Michael Barrett. (University of Melbourne, 1999)

The application of biosolids (sewage sludge) to forests has the potential to increase plantation productivity. Environmental damage may result from pollution of nutrients, heavy metals or pathogens contained in biosolids, leaching of nitrogen (N) to groundwater is of particular concern. This thesis examines the rate of release of N from biosolids, its subsequent fate, and those factors controlling storage and loss of N. Integral to the release of N is the decomposition of biosolids, which is examined through the loss of mass, organic matter and carbon. The potential for increased productivity and environmental risk is assessed through comprehensive N budgeting in the ecosystem. The objectives were addressed through a series of field and laboratory experiments. To compare N dynamics, biosolids were obtained from three sewage treatment plants with contrasting processes (one aerobically- and two anaerobically-digested). The core work was carried out in a major field trial, where biosolids were applied to the forest floor of a 22 year-old Pinus radiata D. Don plantation. The experimental rate of application supplied between 965 and 1425 kg ha-1 of N. More than 85% of the NH4+-N applied in biosolids was volatilised in the first three weeks after application. Subsequent rates of volatilisation were small. The magnitude and temporal patterns were confirmed in a separate study. Volatilisation losses reported in the literature are generally much less, highlighting the variability of losses due to differing biosolids chemistry and environmental conditions at application. About 35% of the organic N was released from anaerobically-digested biosolids in the first year after application, and 54% from the aerobically-digested biosolids. These rates are considerably higher than those used in guidelines of the NSW Environment Protection Authority. There were no significant increases in total N in soil after application, but natural variability in soil precluded detection of increases of the order of 100 kg ha-1. Amounts of NH4+-N in soil increased immediately after application, the size and longevity of increases differing among biosolids. One year after application only very small amounts of inorganic N remained in soil. Throughout the trial, concentrations of NO3--N in soil solution at 60 cm in soil remained consistently below drinking water standards under the anaerobically-digested biosolids and consistently exceeded drinking water standards under the aerobically-digested biosolids. Loss of N in drainage below 60 cm depth in soil in the first year after application was about 20 kg ha-1 under anaerobically-digested biosolids and about 100 kg ha-1 under aerobically-digested biosolids. A controlled incubation study demonstrated that patterns of N mineralisation in the field could not be predicted from laboratory incubations. However relative rates of N mineralisation correlated with amounts of N leached in drainage. Application of biosolids significantly increased tree growth (20 - 34% in basal area) by the second growing season after application. Such a response is likely to be maintained for several years. Rates of volatilisation and mineralisation need to be considered when determining rates of application to ensure that the capacity of soil and plants to store N is not exceeded. Application of anaerobically-digested biosolids at 30 dt ha-1 can increase plantation productivity with minimal risk of groundwater contamination by N. Repeat applications at the same rate concomitant with plantation thinning operations should improve productivity and soil fertility with minimal risk of groundwater contamination.
Nitrogen dynamics after application of biosolids to a Pinus radiata plantation

Robinson, Michael Barrett. (University of Melbourne, 1999)

The application of biosolids (sewage sludge) to forests has the potential to increase plantation productivity. Environmental damage may result from pollution of nutrients, heavy metals or pathogens contained in biosolids, leaching of nitrogen (N) to groundwater is of particular concern. This thesis examines the rate of release of N from biosolids, its subsequent fate, and those factors controlling storage and loss of N. Integral to the release of N is the decomposition of biosolids, which is examined through the loss of mass, organic matter and carbon. The potential for increased productivity and environmental risk is assessed through comprehensive N budgeting in the ecosystem. The objectives were addressed through a series of field and laboratory experiments. To compare N dynamics, biosolids were obtained from three sewage treatment plants with contrasting processes (one aerobically- and two anaerobically-digested). The core work was carried out in a major field trial, where biosolids were applied to the forest floor of a 22 year-old Pinus radiata D. Don plantation. The experimental rate of application supplied between 965 and 1425 kg ha-1 of N. More than 85% of the NH4+-N applied in biosolids was volatilised in the first three weeks after application. Subsequent rates of volatilisation were small. The magnitude and temporal patterns were confirmed in a separate study. Volatilisation losses reported in the literature are generally much less, highlighting the variability of losses due to differing biosolids chemistry and environmental conditions at application. About 35% of the organic N was released from anaerobically-digested biosolids in the first year after application, and 54% from the aerobically-digested biosolids. These rates are considerably higher than those used in guidelines of the NSW Environment Protection Authority. There were no significant increases in total N in soil after application, but natural variability in soil precluded detection of increases of the order of 100 kg ha-1. Amounts of NH4+-N in soil increased immediately after application, the size and longevity of increases differing among biosolids. One year after application only very small amounts of inorganic N remained in soil. Throughout the trial, concentrations of NO3--N in soil solution at 60 cm in soil remained consistently below drinking water standards under the anaerobically-digested biosolids and consistently exceeded drinking water standards under the aerobically-digested biosolids. Loss of N in drainage below 60 cm depth in soil in the first year after application was about 20 kg ha-1 under anaerobically-digested biosolids and about 100 kg ha-1 under aerobically-digested biosolids. A controlled incubation study demonstrated that patterns of N mineralisation in the field could not be predicted from laboratory incubations. However relative rates of N mineralisation correlated with amounts of N leached in drainage. Application of biosolids significantly increased tree growth (20 - 34% in basal area) by the second growing season after application. Such a response is likely to be maintained for several years. Rates of volatilisation and mineralisation need to be considered when determining rates of application to ensure that the capacity of soil and plants to store N is not exceeded. Application of anaerobically-digested biosolids at 30 dt ha-1 can increase plantation productivity with minimal risk of groundwater contamination by N. Repeat applications at the same rate concomitant with plantation thinning operations should improve productivity and soil fertility with minimal risk of groundwater contamination.
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.

School of Agriculture, Food and Ecosystem Sciences - Theses

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