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1
Frost, William E. "The ecology of cereal rust mite Abacarus hystrix (Nalepa) in irrigated perennial dairy pastures in South Australia /". Title page, contents and summary only, 1995. http://web4.library.adelaide.edu.au/theses/09PH/09phf9398.pdf.
Testo completo
2
Doole, Graeme John. "Value of perennial pasture phases in dryland agricultural systems of the eastern-central wheat belt of Western Australia". University of Western Australia. School of Agricultural and Resource Economics, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0213.
Testo completoAbstract (sommario):
Over the past thirty years, price relativities and technological development have motivated an increase in the area of land allocated to cropping, as opposed to pasture production, throughout the central wheat belt of Western Australia. Nevertheless, reducing the proportion of pasture in these rotations has challenged the future productivity of farming systems in this area. First, the frequent application of selective herbicides for weed control in extended cropping rotations has promoted the development of herbicide resistance in a number of major agricultural weeds. Second, the primary use of annual plants has promoted the development of soil salinisation by allowing a significant proportion of rainfall to recharge saline water tables. The inclusion of perennial pasture phases between extended periods of cropping may mitigate or delay these constraints to production through (a) allowing the use of costeffective forms of non-selective weed control, and (b) through creating a buffer of dry soil that absorbs leakage occurring beneath subsequent crops. This study consequently explores the value of including perennial pasture phases in dryland agricultural systems in the eastern-central wheat belt of Western Australia, accounting for benefits related to herbicide resistance and water table management. A novel computational algorithm for the solution of multiple-phase optimal control problems is developed and used to conduct a conceptual analysis of the value of lucerne (Medicago sativa L.) pasture for managing annual ryegrass (Lolium rigidum Gaudin), the primary weed in wheat belt cropping systems. The competitiveness and fecundity of annual ryegrass provide strong economic incentives to maintain a low weed population, irrespective of herbicide-resistance status. Consequently, the ineffectiveness of selective herbicides primarily reduces the profitability of cropping by motivating the adoption of more costly non-selective forms of weed control. The inclusion of lucerne in land-use rotations is only optimal in the presence of severe herbicide resistance given (a) the low efficiency of alternative weed-management practices available during the pasture phase, relative to selective-herbicide application; (b) the significant cost of establishing this perennial pasture; and (c) the high relative profitability of cereal production in the absence of resistance. The value of lucerne, relative to annual pastures, for weed management is explored in greater detail through the use of compressed annealing to optimise a sophisticated simulation model. The profitability of candidate rotations is also manipulated to account for the long-term production losses accruing to the recharge of saline groundwaters that occurs beneath them. Sequences incorporating lucerne are only more profitable than those that include annual pasture at the standard set of parameter values if (a) annual ryegrass is resistant to all selective herbicides, (b) the water table is so shallow (approximately less than 3.5 m deep) that frequent rotation with perennials is required to avert soil salinisation, or (c) sheep production is highly profitable. The value of perennial pasture is sufficient under these circumstances to overcome its high establishment cost. Consistent with intuition, these benefits are reinforced by lower discount rates and higher rates of leakage occurring beneath annual-based systems. Formulation of an effective communication strategy to report these results to producers is justified given the complexity involved in determining the true magnitude of these intertemporal benefits through alternative means, such as field trials.
3
Reeves, Megan. "Milk production from kikuyu (Pennisetum clandestinum) grass pastures". Thesis, Faculty of Veterinary Science, 1997. http://hdl.handle.net/2123/14526.
Testo completo
4
Nurjaya, I. Gusti Made Oka. "Studies on the competitive ability of white clover (Trifolium repens L.) in mixtures with perennial ryegrass (Lolium perenne L.) : the importance of non-structural carbohydrate reserves and plant traits /". Title page, contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09APSP/09apspi11.pdf.
Testo completo
5
Riffkin, Penelope A., of Western Sydney Hawkesbury University e Faculty of Science and Technology. "An assessment of white clover nitrogen fixation in grazed dairy pastures of south-western Victoria". THESIS_FST_xxx_Riffkin_P.xml, 1999. http://handle.uws.edu.au:8081/1959.7/31.
Testo completoAbstract (sommario):
Australia is amongst the more efficient milk producers in the world.Milk production in the region of south-western Victoria relies mainly on rainfed white clover/perennial ryegrass pastures.As the demand for efficient and competitive milk production increases, the value of N2 fixation must be maximised. The objective of this thesis was to assess N2 fixation in grazed dairy pastures in south-western Victoria. Several tests and experiments were conducted and results noted. Studies revealed low white clover yields to be the major factor limiting N2 fixation in the region. For N2 fixation to have a significant impact on pasture quality and production, problems associated with legume persistence need to be addressed. Strategies may include the breeding of white clover cultivars with greater tolerance to water stress, improved winter production and increased competitiveness with companion species. Alternatively, the introduction of different legume species, better suited to the environment, may be appropriate. Where N2 fixation is unlikely to satisfy N demands, it may be necessary to introduce the strategic use of supplementary feeds or nitrogenous fertilisers. However, this would need to be carefully considered to ensure high input costs did not jeopardise the competitive advantage of low input pasture-based systemsMasters Thesis
6
Valizadeh, Reza. "Summer nutrition of sheep based on residues of annual crops and medic pastures". Title page, contents and abstract only, 1994. http://web4.library.adelaide.edu.au/theses/09PH/09phv172.pdf.
Testo completo
7
Dalby, Paul Reginald. "Competition between earthworms in high rainfall pastures in the Mt. Lofty Ranges, South Australia". Title page, contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phd137.pdf.
Testo completoAbstract (sommario):
Copy of author's previously published work inserted. Bibliography: leaves 261-306. The objectives of the project were: i. to determine whether there are competitive interactions between Aporrectodea trapezoides and A. caliginosa and A. rosea.--ii. to investigate compeditive interactions between A. calignosa, Microscolex dubius and A. trapezoides.--iii . to determine the likely impact of A. longa on soil fauna, especially the native earthworm, Gemascolex lateralis, in native ecosystems.
8
Johnston, William Henry, University of Western Sydney, of Science Technology and Environment College e School of Environment and Agriculture. "The role of Eragrostis curvula (Schrad.) Nees. complex in temperate pastures in southeastern Australia". THESIS_CSTE_EAG_Johnston_W.xml, 2003. http://handle.uws.edu.au:8081/1959.7/29.
Testo completoAbstract (sommario):
This thesis examines the hypothesis that, in southern New South Wales and northeast Victoria, Australia, palatable taxa of E. curvula offer advantages that complement those of the species that are traditionally sown in temperate pastures in a landscape context.This hypothesis was based on a review of literature showing that, prior to European settlement, the vegetation, the landscape and the climate were broadly in balance, and the wateruse pattern of the vegetation of southeastern Australia resulted in water being used more-or-less completely by the end of summer. This maximised the capacity of the soil to take up and store water during autumn and winter.Three grazing experiments and one spaced-plant species evaluation study were used to assess the role of summer-growing, C4 Eragrostis curvula in pastures in the temperate zone of southeastern Australia.Issues relating to pasture production and the productivity of wool-growing sheep were investigated. Factors affecting the sustainability of the pastures and their potential on and off site impacts were emphasised.Modelling was used to explore issues of water use, arising from the grazing experiments. It is concluded that the persistence, production, water use patterns, and the adaptability of palatable varieties of E. curvula make it a useful and complementary addition to the range of species that are currently available for use as sown pastures in southern Australia.Doctor of Philosophy (PhD)
9
Johnston, William Henry. "The role of Eragrostis curvula (Schrad.) Nees. complex in temperate pastures in southeastern Australia /". View thesis View thesis, 2003. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030506.100204/index.html.
Testo completo
10
Riffkin, Penelope A. "An assessment of white clover nitrogen fixation in grazed dairy pastures of south-western Victoria". Thesis, [Richmond, N.S.W.] : University of Western Sydney, Hawkesbury, 1999. http://handle.uws.edu.au:8081/1959.7/31.
Testo completoAbstract (sommario):
Australia is amongst the more efficient milk producers in the world.Milk production in the region of south-western Victoria relies mainly on rainfed white clover/perennial ryegrass pastures.As the demand for efficient and competitive milk production increases, the value of N2 fixation must be maximised. The objective of this thesis was to assess N2 fixation in grazed dairy pastures in south-western Victoria. Several tests and experiments were conducted and results noted. Studies revealed low white clover yields to be the major factor limiting N2 fixation in the region. For N2 fixation to have a significant impact on pasture quality and production, problems associated with legume persistence need to be addressed. Strategies may include the breeding of white clover cultivars with greater tolerance to water stress, improved winter production and increased competitiveness with companion species. Alternatively, the introduction of different legume species, better suited to the environment, may be appropriate. Where N2 fixation is unlikely to satisfy N demands, it may be necessary to introduce the strategic use of supplementary feeds or nitrogenous fertilisers. However, this would need to be carefully considered to ensure high input costs did not jeopardise the competitive advantage of low input pasture-based systems
11
Mayberry, Dianne. "Getting into the guts of a salty problem : poor animal production from saltbush pastures is due to inefficient rumen fermentation". University of Western Australia. School of Animal Biology, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0071.
Testo completoAbstract (sommario):
The main hypothesis tested in this thesis was that poor animal production from saltbush pastures is due to the negative effects of high sodium chloride (NaCl) and potassium chloride (KCl) on the ruminal environment, and subsequent effects on microbial populations and products of rumen fermentation. This main hypothesis was tested in two experiments. In the first experiment (Chapter Four) the effects of saltbush and a formulated high-salt diet on the ruminal environment and microbial populations were measured over 24-hours following feeding. Feeding both the saltbush and high-salt diet increased the salinity of the rumen fluid, but the formulated high-salt diet caused a decrease in ruminal pH while the saltbush caused an increase. This resulted in differences in the composition of the ruminal microbial populations between the sheep fed different diets. In the second experiment (Chapter Five) the effects of saltbush and a formulated highsalt diet on rumen fermentation were measured. Sheep fed saltbush had inefficient rumen fermentation and this was only partially explained by the high salt content of the diet. Diets containing high levels of NaCl and KCl provided low levels of net energy to sheep, but sheep fed saltbush lost more energy as methane and faecal energy compared to sheep fed the formulated high-salt diet. Inefficient rumen fermentation could help to explain poor animal production from saltbush pastures. Energy supplements such as barley grain can improve the value of saltbush pastures as feed for sheep, but there is no information on how much supplement is required. A third experiment (Chapter Six) was designed to test the hypothesis that there would be an optimal amount of barley required to improve the efficiency of rumen fermentation in sheep fed saltbush. Barley and straw were combined in a pellet and substituted for saltbush at 0, 20, 40, 60, 80 and 100% of the maintenance ration. Feeding barley and straw improved the efficiency of rumen fermentation in sheep fed saltbush, with an optimal level of supplementation at 60% of the maintenance diet. This is likely to be lower (approximately 20% of maintenance) if barley is fed without straw.
12
Sounness, Marcus Neil. "Alternative grazing systems and pasture types for the South West of Western Australia : a bio-economic analysis". University of Western Australia. School of Agricultural and Resource Economics, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0054.
Testo completoAbstract (sommario):
Alternative grazing systems and pasture types for wool production in the south west of Western Australia were analysed using bio-economic modelling techniques in order to determine their relative productivity and profitability. After reviewing the experimental and modelling literature on perennial pastures and grazing systems, seven case studies of farmers were conducted in order to investigate the practical application of innovative grazing systems and use of perennial pastures. Together these case studies provided information for identifying relevant variables and for calibrating the modelling work which followed. The core of the work lies in a bio-economic model for investigating the comparative value of the three grazing systems and two pasture families mentioned above. A baseline scenario using currently available and reliable scientific data provides baseline results, after which a number of sensitivity analyses provide further insights using variations of four key parameters: persistence, heterogeneity, water soluble carbohydrates, and increased losses. Results show that perennial pastures are in the studied region more profitable than annual pastures. Under current baseline conditions, continuous grazing with perennial pastures is the most profitable enterprise, but this superiority is not robust under parameter variations defined by other scenarios. The more robust solution in terms of enterprise profitability is cell grazing with perennial pastures. The results indicate that intensive grazing systems such as cell grazing have the potential to substantially increase the profitability of grazing operations on perennial pasture. This result is an encouraging one in light of its implications for water uptake and salinity control. It means that economics and land care can go hand in hand, rather than be competitive. It is to be noted that it is the choice of the grazing system in combination with the pasture species, rather then the pasture species itself, that allows for such complementarity between economics and sustainable land use. This research shows that if farmers adopt practices such as cell grazing they may be able to increase the area that they can profitably plant to perennial pasture thus reducing the impacts of dryland salinity. This finding is consistent with the findings of the case studies where the farmers perceived that, provided grazing was planned, increasing the intensity of their grazing management and the perenniallity of their pastures would result in an increase in the profitability of their grazing operation. As a result this research helps to bridge a gap which has existed in this area of research, between the results of scientific research and those reported in practice.
13
Ranjbar, Nezhad Isfahani Shahab. "Lameness in Pasture-Based Dairy Farms in NSW, Australia". Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/17084.
Testo completoAbstract (sommario):
Lameness is one of the most important welfare issues in the dairy industry with all cows being at risk during their productive life. It decreases milk production, compromises fertility and increases the chance of being culled. To reduce the likelihood of lameness in cows, a thorough knowledge of the risk factors is essential. Risk factors have been found to differ between farming systems which highlighted the need for a project to identify risk factors of lameness in NSW pasture-based dairies. The thesis reviews the literature on risk factors pertaining to lameness in dairy cattle worldwide with focus on the main aspects of lameness regarding pasture-based dairy farming. First study investigates the prevalence and the potential risk factors for lameness in 62 pasture-based dairies in NSW with the aim to identify risk factors for lameness and to provide the industry with an indication as to the relative contribution of these risks so that dairy producers could allocate their resources to areas most likely to have the greatest impact when planning a prevention strategy. The data gathered through the interviews with farmers focuses on their perception of lameness in their herds. International experience suggests farmers’ perception of lameness are less than the true prevalence, which was proved to be the case in NSW, Australia. The reduced perception of lameness appears to be associated with delayed treatment and poor treatment outcome. Treatment outcomes may be further compromised by almost 30% of farmers or farm staff not having undergone training as to how to effectively trim and treat lame cows. The final study gathers data on wooden hoof blocks commonly used in treatment of lame cows. This study assesses the association between wood density, longevity, and wear characteristics of wooden hoof blocks. It was found that the hardness of the commercial blocks is insufficient to provide an appropriate duration of protection for healing claw lesions.
14
Maddern, Rowan John. "Low water-soluble superphosphate fertiliser for pasture production in south-western Australia". Thesis, Curtin University, 2016. http://hdl.handle.net/20.500.11937/2242.
Testo completoAbstract (sommario):
Single superphosphate is derived from chemically treating rock phosphate into relative proportions of monobasic, dibasic and tribasic calcium phosphate to produce a commonly used source of phosphorus fertiliser for pasture systems. The leaching of phosphorus on susceptible soil types contributes to eutrophication and environmental damage. By modifying the chemistry of single superphosphate to match a soils phosphorus binding index and rainfall conditions, pasture dry matter yield can be maintained and leaching of phosphorus significantly reduced.
15
McLaughlin, Michael John. "Phosphorus cycling in soil under wheat-pasture rotations /". Title page, contents and summary only, 1986. http://web4.library.adelaide.edu.au/theses/09PH/09phm1615.pdf.
Testo completo
16
Brown, Peter Robert, e n/a. "Pasture response following rabbit control on grazing land". University of Canberra. Resource & Environmental Science, 1993. http://erl.canberra.edu.au./public/adt-AUC20061113.144813.
Testo completoAbstract (sommario):
The experiments described in this thesis were designed to assess changes in pasture
dynamics (biomass and species composition of pasture) of grazing land on the Southern
Tablelands of ACT and NSW, after 16 combinations of rabbit control treatments had been
applied. The rabbit control performed by CSIRO Division of Wildlife and Ecology
consisted of all combinations of presence-absence of Poisoning (using sodium
monofluoroacetate, 1080: POIS), Ripping (ripping warrens using a tractor fitted with
ripping tynes: RIP), Fumigation (pressure fumigation using chloropicrin: FUM) and
repeated follow-up fumigation (using phostoxin pellets one, six and eighteen months after
completion of the initial treatment: ANN). The pasture was assessed before treatments
were applied, and every six months after rabbit control treatments. Treatment
combinations were assigned randomly in a 24 factorial design on a total of 32 sites.
There was a significant increase of pasture biomass at the RIP+ANN treatment at
post-treatment sample 5. The analysis of covariance did not detect any other significant
increase or decrease of pasture biomass for any rabbit control treatment, at any posttreatment
sample.
A significant increase of grass species occurred for the treatments of
POIS+RIP+FUM, POIS and RIP+ANN for the post-treatment samples of 1, 3 and 5
respectively. There was a significant increase of thistles at the rabbit control treatments of
POIS+RIP+FUM+ANN (post-treatment sample 1), RIP, ANN, RIP+FUM,
RIP+FUM+ANN and POIS+RIP+FUM+ANN (post-treatment sample 3) and RIP and
FUM+ANN (post-treatment sample 5). A significant increase of weeds occurred at FUM
(post-treatment sample 3) and at FUM+ANN (post-treatment sample 5). No significant
changes in the amount of herbs or legumes was apparent for any rabbit control treatment or
post-treatment sample. There were no significant decreases for any species group. Except
for the significant results for post-treatment sample 1, all significant increases of biomass
for any species group occurred during spring (post-treatment sample 3 and 5) which
suggests a growth phase during spring then subsequent dieback (particularly for thistles and
weeds), as any change was not detected in the following autumn sample. No strong trend
is evident for any particular rabbit control treatments, or any combination of treatments.
Analysis of covariance revealed that the rabbit control treatment of RIP+ANN
showed significant increases in both total biomass of pasture and grass biomass during
post-treatment sample 5. This treatment reduced the number of active entrances the most.
Significant positive correlations were found between pasture biomass (total) with
grass, herb, legume, thistle and weed species groups. Significant negative correlations
between grass biomass and the number of active entrances were found when the rabbit
control had been highly effective in reducing the number of active entrances. When rabbit
control had not been very successful, there was a significant positive but low correlation
with the number of active entrances. There was no significant relationship between the
number of active entrances with the weight of rabbit dung pellets. It is reasoned that they
are different measures of rabbit abundance. More rabbit dung pellets were found closer to
the warren than further away from the warren, but there was no correlation between rabbit
dung and pasture biomass.
Rainfall was above average for most of the experiment, biomass increased
accordingly, and rabbit control was highly successful. The resulting changes in the pasture
were difficult to detect, although some increases in species composition groups occurred.
It is reasoned that the changes observed are partly attributable to seasonal conditions, and
to high rainfall. Grazing by domestic animals, sheep and cattle, had been found to be
consistent throughout the experiment.
17
Crawford, Michael Cameron. "Quantification of the belowground inputs of organic carbon by the annual pasture legume barrel medic (Medicago truncatula Gaertn.)". Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phc8988.pdf.
Testo completoAbstract (sommario):
Bibliography: leaves 164-193. This study aims to quantify the belowground input of organic carbon by barrel medic using techniques that account for root death and decomposition as well as root secretion and exudation. It also investigates the effect of defoliation on carbon allocation within the plant so as to determine the potential for optimising carbon input to the soil through grazing management.
18
Abdelsayed, Mary. "Quantitative Genetic Analysis of Extended Lactation and Lactation Persistency In Australian Dairy Cattle on Pasture Based Systems". Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/13994.
Testo completoAbstract (sommario):
In the Australian dairy industry, and in particular Victoria, there has been a shift away from seasonally concentrated calving patterns. Reasons for such a shift stem largely from improved feeding of cows with year round feed supplies, and the introduction of new germplasm from North American Holstein Friesian animals into some Australian dairy herds. Such impacts have resulted in an increase in the phenotypic and genetic potential of cows to produce more milk and be milked for longer than the standard 305 days under seasonal calving systems. The increase in high output cows has come at an associated cost with a national decrease in reproductive performance and many highly productive cows being prematurely culled for failing to get in calf. One strategy of interest to the dairy industry is for high-producing cows being mated out of season and then carried over and milked for an extra 6 months (18 month calving interval). In Australia this is regarded as the most optimal and economical method on pasture-based systems. Limited information was available about the potential for genetic improvement of extended lactation under the Australian dairy system, which led to the objectives of this thesis. A very large amount of data with over 158 million test-day records was available to examine the scope for genetic improvement in extended lactation in the Australian dairy industry. A data handling pipeline was developed to assist in analysing and editing large scale industry test day records. Variation in Australian dairy cattle in respect to their lactation curves over an extended lactation was explored and derived traits obtained that were then used in the genetic analysis using mixed model methodology. The Wood model was fitted to milk yield records divided into 8 random subsets of 1 million pure Holstein cows with 20 million test-day records. Two traits of interest, namely persistency and extended lactation, were quantified and relevant descriptive traits derived. Variation among cows in their ability to maintain high production over a longer period of time was evident and a representation of the shape of average lactation curves in Australian dairy cows was presented. Findings showed that milk production during the extended lactation phase (from day 305 to day 610 of lactation) was on average equivalent to 40% of the production of the first 305 days of lactation (standard lactation) with an average milk yield of 8,887 L over the extended lactation. In terms of lactation persistency, 50% of peak production is maintained up to day 305. Estimates of heritability for milk, fat and protein yield under extended lactation (0.09-0.06±0.004) and lactation persistency (0.06-0.1±0.004) were low, while the cows’ repeatability for extended lactation and lactation persistency milk traits (0.20) was higher by comparison. Such findings indicate the potential for early cow performance to be used as an indicator for a cow’s successive lactation performance. Extended lactation and lactation persistency were found to be highly correlated to each other (genetic 0.60-0.98 and phenotypic 0.68-0.93), but not with the other economically important traits of milk, fat and protein yield (-0.05-0.1). This suggests that selection for increased extended lactation will not adversely impact on economically important and highly selected traits, namely cumulative 305 day yields and the Australian Selection Index (ASI). Extended lactation measured as a standardised ratio trait automatically adjusts for high peak yield. Producers selecting on this trait do not favour selecting cows with higher peak yields yet maintaining peak production over another 300 days in milk. In addition, extended lactation can be incorporated with cumulative 305 day milk yields and lactation persistency in a selection index in a designed breeding program. Estimated breeding values (EBVs) were generated for extended lactation and lactation persistency for milk, fat and protein yields, to assist with the selection of cows and bulls. Genetic trends showed no change till early 1990, followed by a steady increase (1genetic SD) in EBVs for extended lactation characteristics in the last 20 years. This increase is potentially a reflection of the increased selection for milk production and introduction of new germplasm from North American Holstein Friesian cattle into Australian herds. The research presented in this thesis will provide the Australian dairy industry with the breeding tools to enable selection of bulls to produce cows that are best suited to extended lactation in pasture-based systems. It has also contributed to the understanding of the genetics of extended lactation and lactation persistency that can be applied to other breeds in the Australian herd, and opened avenues for genomic predictions for these traits.
19
Yeap, Simon G. H. "Investigating the impacts of groundwater on soil properties and pasture nutrition in irrigated agriculture, Pilbara region of Western Australia". Thesis, Yeap, Simon G.H. (2014) Investigating the impacts of groundwater on soil properties and pasture nutrition in irrigated agriculture, Pilbara region of Western Australia. Honours thesis, Murdoch University, 2014. https://researchrepository.murdoch.edu.au/id/eprint/32100/.
Testo completoAbstract (sommario):
Dewatering of groundwater systems has become a common practice for iron ore mining in the Pilbara region of Western Australia. While the discharge of surplus water to local tributaries and re-injection into the aquifer are widely practiced, the re-use of this water for irrigated forages is an innovative solution. However, the chemistry of the groundwater and the impacts on soil properties from long-term application of groundwater need to be assessed.
Surplus water from the Marandoo iron ore mine is utilised to irrigate Rhodes grass (Chloris gayana) for hay production at the Hamersley Agricultural Project (HAP). After amendment with nutrients, the irrigation water was slightly alkaline (pH 8.0) and slightly brackish-sodic (total dissolved solids, TDS, of 580 mg/L) with Ca (61 mg/L), Mg (50 mg/L) and Na (43 mg/L) as the dominant cations and bicarbonate (270 mg/L) as the dominant anion. This study aims to identify the implications of irrigation with this water for pasture production and soil management.
Following the commencement of irrigation in October 2012, significant changes and trends in soil properties and leaf nutrient composition of C. gayana were examined over a 15 month period, based on a quarterly sampling program across 10 centre-pivot irrigation systems. Analysis initially showed that the continuation of current trends could result in: (1) increases in soil sodicity, since ESP levels had exceeded 5% at 0-10 cm and 7% at 20-30 cm, and (2) alkalinisation, such that the soil pH is predicted to reach ~8.2. However, subsequent analysis with pre-washed soil samples to remove soluble salts indicated that irrigation had not caused a measureable change in the ESP and hence no change in the sodicity of HAP soils.
Nonetheless, the geochemical model WEB-PHREEQ suggests the precipitation of carbonate, (hydr)oxide and phosphate (apatite) minerals of Ca, Mg, Fe and Mn could also impose a risk for immobilising nutrients applied from irrigation water, given suitable conditions for nucleation and crystal growth. Moreover, changes in the relative abundance of soil exchangeable cations may also adversely affect plant nutritional balance whereby exchangeable Mg2+ as a percentage of cation exchange capacity has significantly increased while the percentages of exchangeable Ca2+ and K+ have significantly decreased.
In the next 20 years, based on the estimated duration of the HAP, soil alkalinisation could emerge as a problem by suppressing the availability of various nutrients. Future monitoring and research, in conjunction with effective irrigation and soil management practice, will hence be imperative to ensure long-term sustainability of pasture production at the HAP, as well as for rehabilitation of soils after decommissioning.
20
Salam, Kawsar Parveen. "Improving the fit of new annual pasture legumes in Western Australian farming systems: experience from Cadiz and Casbah". Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/1953.
Testo completoAbstract (sommario):
Annual pasture legumes (APLs) are important in Western Australian farming systems, with subterranean clovers and annual medics being dominant. However, due to potential environmental, economic and biological constraints of these species, alternatives have been sought, with a second generation of new species being introduced since 1991. Despite the views of researchers about the advantages in WA conditions of the newly released annual pasture legumes over traditional pastures, there is a perception by some industry decision makers that their level of adoption has been lower than expected. However, there was not a good method for evaluating the level of adoption. The aim of this study was therefore to enhance understanding of how to improve the fit of new annual pasture legumes in Western Australian farming systems, taking two pastures, French serradella (Ornithopus sativus) cv. Cadiz and Biserrula (Biserrula Pelecinus) cv. Casbah (Hereafter, will be referred to as Cadiz and Casbah.), as examples.The objectives of the study were implemented in four steps. In step one, a framework, built on a three-tier hierarchy (broad adoption potential or BAP, broad attainable adoption potential or BAAP, and maximum attainable adoption potential or MAAP) was developed based on the agro-ecological suitability of the annual pasture legumes. BAP was calculated from the amount of suitable land in terms of soil and rainfall requirements for an APL. The BAAP was calculated by multiplying BAP with two coefficients related to the proportion of cropping area within a geographic region, and the crop-pasture ratio within the cropping area. The MAAP was calculated by multiplying BAAP with a coefficient related to the certainty of a successful pasture-growing season. This coefficient was derived from a Microsoft-Excell®-based Climate Reliability Calculator particularly developed for this study. The broad attainable adoption potentials (BAAP) for Cadiz and Casbah were calculated as 1.67 M ha and 1.18 M ha, respectively. These figures were about 81% less than the calculated broad adoption potential (BAP). The maximum attainable adoption potentials (MAAP) for Cadiz and Casbah in Western Australian cropping-belt were calculated as 0.99 and 0.89 M ha, respectively.In step two, a survey was conducted to understand the salient issues that farmers consider in relation to adopting a new annual pasture legume for their farming systems. An open-ended question was used for them for the attributes they desired for their ‘dream’ pasture. Questions were also asked about their experiences of strengths and weaknesses for Cadiz and Casbah. Responses were analysed using the principles of ‘grounded theory’. Furthermore, based on farmers’ perceptions, an APL-characteristics framework was developed for Western Australia. The framework consisted of six attributes of a pasture. They are, in order of importance calculated from the percent of farmers responses: superiority in establishment and growth (79%), ability in supplying quality feed (49%), improved potential in controlling weeds (38%), adaptability in broader agro-ecological horizon (36%), tolerant to major insect-pests (20%), and inexpensive (15%). Many farmers desired a combination of these components rather than just a single component. The two test APLs, Cadiz and Casbah, were compared under this framework based on the responses of the farmers.In the third step, using farmers’ perceptions of the salient attributes and other variables, an empirical model was developed to predict the likely adoption of any annual pasture legume in Western Australian farming systems. The model consisted of the product of two components, AAAR and TRMAP. The AAAR was the averaged annual adoption rate (as the percentage of all pastures grown in Western Australia) of the APL. TRMAP is the time, in years, required to reach the maximum adoption potential of the APL. The AAAR was related to the agronomic characteristics of the APL (the three most wanted characteristics by farmers, i.e. establishment and growth, feed supply and quality and weed control) and an ‘inter-competition’ factor, whereas the TRMAP was attributed to its scope of adaptation. Both AAAR and TRAMP were essentially regression models. The model performed well when tested independently for Cadiz and Casbah using inputs from two different sources, i.e. breeders and farmers. In the final step, the model was applied to predict the adoption of Cadiz and Casbah using inputs from breeders and farmers in order to understand what level of adoption breeders would have expected and to what extent farmers would support the breeders’ view. Results showed that breeders were expecting Cadiz and Casbah would be adopted in about 32% and 22% of their potential areas (MAAP) compared to the achieved adoption of 23% for Cadiz and 20% for Casbah, respectively.On the other hand, model output using farmers’ evaluation scores indicated that the adoption would be 20% for Cadiz and 19% for Casbah, which is much closer to the achieved adoption level. The difference between breeders’ expectation and farmers’ evaluation on adoption potential of Cadiz and Casbah was due to differences in evaluation scores provided by the two groups on different pasture characteristics in relation to establishment and growth, weed control and feed supply and quality. Some of the pasture characteristics desired by the farmers, such as reliable regeneration, seed settings, easy establishment, general vigor, good chemical tolerance, good feed supply and quality, suitable for wide range of soils, good insect tolerance are not commonly present when Cadiz and Casbah are grown in the farming environments.Two issues for further consideration if the adoption levels of Cadiz and Casbah were to be increased in WA farming systems are: decreasing the knowledge gap among farmers on tactical management of APLs though extension, and improved pasture characteristics through the breeding/selection process. Furthermore, this study designed a system consisting of three major components: the maximum attainable adoption potential (MAAP), the annual pasture legume characteristics framework (APL-characteristics for Western Australia) and achievable adoption potential (AAP). This system acts as a common platform - where breeders, farmers, extension specialists and policy makers could work as a team towards improving the fit of annual pasture legumes, and potentially other crops if the required supporting information was collected, in Western Australian farming systems.
21
McIntyre, Daniel Lester. "Application of high resolution remote sensing to detect and map the pasture weed Paterson’s curse (Echium plantagineum) in Western Australia". Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/1511.
Testo completoAbstract (sommario):
This study investigated the utility of three types of remotely sensed data (field spectroscopy, airborne multispectral and satellite hyperspectral) for detecting and mapping Paterson’s curse (Echium plantagineum) in the Wheatbelt Region of Western Australia. Using different classification, statistical and quantitative validation approaches, the study found that spectral resolution and timing of image capture were the most important factors for discriminating Paterson’s curse and producing acceptable levels of mapping accuracy.
22
Burns, Kit Alexander. "Characterisation of rhizobia for the new annual pasture legume Scorpiurus muricatus targeted for medium-to-low rainfall areas of southern Australia". Thesis, Burns, Kit Alexander (2019) Characterisation of rhizobia for the new annual pasture legume Scorpiurus muricatus targeted for medium-to-low rainfall areas of southern Australia. Honours thesis, Murdoch University, 2019. https://researchrepository.murdoch.edu.au/id/eprint/53975/.
Testo completoAbstract (sommario):
Legumes play an integral role in increasing agricultural productivity, particularly in low input agricultural systems in Australia, due to their ability to form symbiotic interactions with a group of soil bacteria called rhizobia. However, in medium-to-low rainfall areas of southern Australia, there is a lack of suitable annual pasture legumes, which is limiting agricultural productivity and profitability in these farming systems. Scorpiurus muricatus is an annual legume from the Mediterranean which possesses high nutritive value and palatability for livestock, is high yielding, capable of self-seeding and is well-adapted to hot and dry summers. As such, S. muricatus is currently being evaluated as a new pasture legume for southern Australia. Crucial to the success of introducing this legume will be the availability of a highly effective rhizobial inoculant strain. This thesis therefore sought to characterise the phylogeny, free-living and symbiotic phenotype of a range of bacteria isolated from Scorpiurus spp.
A total of 19 strains were investigated, with 16s rRNA sequencing demonstrating that 18 of these strains belonged to the genus Mesorhizobium, with the remaining strain (WSM1184) most closely related to Agrobacterium tumefaciens. Analysis of nifH and nodC symbiosis genes further showed that the characterised Mesorhizobium strains generally shared highly similar sequences for these loci, indicating a comparatively high degree of genetic similarity. In particular, WSM1343 (isolated from Scorpiurus sulcatus growing in Morocco) and WSM1386 (isolated from S. sulcatus in Manjimup, Western Australia) were shown to share highly similar symbiosis genes, but divergent 16S rRNA genes, suggesting the possibility that these strains may contain symbiosis genes on mobile Integrative and Conjugative Elements (ICEs).
While the temperature tolerance and apparent optimum growth temperature of the test strains of 28°C was consistent with that commonly reported for Mesorhizobium spp., their growth rate was atypical for this genus, with 15 of the 18 strains having a growth rate on YMA at 28°C slower than that generally described for Mesorhizobium. This slower growth rate may be a common feature of rhizobia from S. muricatus nodules and therefore should be considered when isolating organisms from this legume.
Symbiotic effectiveness experiments showed all Mesorhizobium strains nodulated S. muricatus and fixed N2 on this host, with the most effective strain producing 67.5% of the mean shoot dry weight of the N-fed control plants. Host range experiments demonstrated a subset of the Mesorhizobium strains nodulate existing Australian commercial pasture legumes Biserrula pelecinus and Lotus corniculatus, with the effectiveness data suggesting these strains fix N2 poorly on both hosts. In contrast, none of the strains tested were able to nodulate the grain legume Cicer arietinum.
While this thesis has characterised the phylogeny, free-living and symbiotic phenotype of a range of S. muricatus microsymbionts, further work is required before a suitable commercial inoculant strain can be recommended for this pasture legume. First, all the strains tested in this thesis were isolated from S. sulcatus plants or soils with Scorpiurus spp. present, rather than S. muricatus and it is not known whether strains from either species are cross-compatible for effective N2 fixation. Future studies may therefore locate more effective N2-fixing rhizobia for S. muricatus by isolating microsymbionts from this host in the field. Second, experiments testing the ability of commercial inoculants for already-established pasture legumes B. pelecinus (WSM1497), Lotus sp. (SU343, CC829) and the grain legume C. arietinum (CC1192) to nodulate and fix N2 on S. muricatus need to be conducted to determine whether these inoculants will interact with this legume. Finally, the data strongly suggest that S. muricatus-nodulating Mesorhizobium spp. may contain symbiosis genes on mobile symbiosis ICEs. Given that the phenomenon of ICE transfer has led to the evolution of poorly effective microsymbionts for B. pelecinus, it is imperative that these S. muricatus strains be interrogated for the presence and transfer of symbiosis ICEs, in order to manage this mobility in any future commercial inoculant strain that is released for this pasture legume species.
23
McDonald, Kathi. "Variation in morphology, salinity and waterlogging tolerance and resource allocation in strawberry clover (Trifolium fragiferum L.) : implications for its use in mildly saline soils in southern Australian farming systems". University of Western Australia. School of Plant Biology, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0105.
Testo completoAbstract (sommario):
[Truncated abstract] In southern Australian farming systems the replacement of deep-rooted perennial native vegetation with shallow-rooted annual crops and pastures has resulted in rising groundwater tables and an increased incidence of dryland salinity. It has been suggested that to address this issue by restoring hydrological balance, large areas of agricultural land need to be vegetated with perennial plants. One of the most agriculturally productive ways to do this is to introduce perennial pastures, both into upslope groundwater
24
Siddiqi, Muhammad Junaid. "Remote sensing and GIS techniques for monitoring and predicting land degradation and impacts of engineering solutions in an area". Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/2427.
Testo completoAbstract (sommario):
Salinity, waterlogging and drought are major causes of land degradation and serious threats to sustainable agricultural productivity in the south-west agricultural region of Western Australia (WA). The spectral signatures of pasture plants under drought, waterlogging and nutrient deficiency were examined in a greenhouse study using both a field and an analytical laboratory spectrometer (400 to 2,500 nm wavelength). Drought stress group (RWC, 39.9%) has the highest reflectance of 48.2%, waterlogging group (RWC, 49.7%) with a magnitude of 43.1% reflectance and control group (RWC, 61.5%) has the lowest of 41.9%. The highest separability based on magnitude among control, waterlogging and drought stress groups is located at reflection band at 1,666 nm, 1,818 nm and 2,216 nm and at 1,450 nm absorption bands. Remote sensing and GIS techniques were used to predict risks of soil salinity and waterlogging in the study area. Time-sequenced Landsat TM satellite data and groundwater data were analysed to delineate areas where major changes in soil salinity, waterlogging have taken place before and after engineering interventions of deep drains.The rainfall data analysis of all cities in the south-west of Western Australia indicate that annual rainfall has been decreasing since 1969 for some cities in the region and rainfall is decreasing in some cities since 1975. The winter season rainfall shows a downward trend and summer season rainfall shows an upward trend linked to an increase in the frequency of summer storm events in the south-west, in the Wheatbelt and in the east of Western Australia. The annual rainfall and summer season rainfalls have been increasing in the north of Western Australia and both annual rainfall and summer season rainfalls show an increasing trend. Climate change was studied for northern, eastern, Wheatbelt and south-west of WA and its impacts of on surface runoff, groundwater recharge, and land degradation were studied.Deep open drains were monitored in the two major drainage districts of Narembeen and Dumbleyung in Wheatbelt of Western Australia. The efficacy of drains in mitigating the problems of waterlogging and salinity in the area was studied. Information on monitoring of drains in six coastal districts in Western Australia, from Australia and other countries was collated and a coastal drainage best management practices ‘BMP Toolbox’ has been developed.
25
Chaichi, Mohammad Reza. "Grazing management of annual medic pastures / by Mohammad Reza Chaichi". 1995. http://hdl.handle.net/2440/18733.
Testo completoAbstract (sommario):
Bibliography: leaves 300-321.xiii, 321 leaves [11] leaves of plates : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
This thesis aims to extend knowledge and understanding of the seed-seedling dynamics and productivity of annual Medicago pastures. In particular this study concentrates on the impact of grazing by sheep on Medicago pasture herbage and seed production and sheep body weight gains.
Thesis (Ph.D.)--University of Adelaide, Depts. of Agronomy and Farming Systems and Plant Science, 1997
26
Frost, William E. "The ecology of cereal rust mite Abacarus hystrix (Nalepa) in irrigated perennial dairy pastures in South Australia / by William E. Frost". Thesis, 1995. http://hdl.handle.net/2440/18667.
Testo completo
27
Valizadeh, Reza. "Summer nutrition of sheep based on residues of annual crops and medic pastures / by Reza Valizadeh". Thesis, 1994. http://hdl.handle.net/2440/21502.
Testo completoAbstract (sommario):
Bibliography: leaves 259-291.xiii, 291 leaves, [8 leaves of col. plates] : ill. (some col.) ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, Faculty of Agricultural and Natural Resource Sciences,1994
28
Dougherty, Warwick John. "The mobilisation of soil phosphorus in surface runoff from intensively managed pastures in South-East Australia". 2006. http://hdl.handle.net/2440/37852.
Testo completoAbstract (sommario):
The application of substantial quantities of phosphorus (P) has been required to increase productivity on many Australian soils. Unfortunately, these applications have often resulted in increased concentrations of P in surface runoff that contributes to excessive algal growth in surface waters and consequently a decline in their quality. The concentrations of P in runoff from intensively managed pastures are often high (1-5 mg/L) and typically at least an order of magnitude higher than water quality targets. Although a substantial amount of research has been devoted to the problem of P accumulation and mobilisation in arable systems ( in which P is typically mobilised by the action of raindrop impact and subsequently transported in particulate form ), there has been substantially less research in intensively managed pasture systems. Consequently, there is a paucity of knowledge concerning the fundamental processes and factors responsible for P in runoff from these systems and a dearth of truly effective remedial strategies. In this thesis, the accumulation of P in soil under intensively managed pastures used for dairying and the processes responsible for its mobilisation in surface runoff were investigated. This research was undertaken at two research sites in South - east Australia, i.e. Camden in New South Wales and Flaxley in South Australia. A number of factors relating to scale and hydrology may influence the processes of P mobilisation and its concentration in runoff. A comparison was made of the forms and concentrations of P in runoff between a typical rainfall simulation methodology and large runoff plots. The effect of rainfall intensity on the forms and concentrations of P was also investigated. The concentrations of P in runoff from small - scale, high - intensity rainfall simulations were on average 33 % lower than those from large plots ( approximating hillslopes ) although the processes of mobilisation ( as evidenced by runoff P forms ) were similar. Increasing rainfall intensity resulted in decreasing P concentrations, but similar forms of P. It was hypothesised that changes in hydrological characteristics ( residence time and depth of runoff ) were responsible for the differences in the P concentrations. A model of P mobilisation ( incorporating hydrological and P - release characteristics ) was developed and shown to successfully predict runoff P concentrations under a range of rainfall intensities. These findings and the subsequent model were used in the successful modelling of landscape scale nutrient exports based on rainfall simulation data as part of a separate, but complementary project. There is anecdotal evidence to suggest that Australian soils are relatively ' leaky ' in terms of P in runoff compared to soils overseas. Consequently, comparisons of the labile soil P characteristics and soil P - runoff P relationships were made between Australian soils and soils of similar fertility from the USA, UK and New Zealand ( using both experimental data and data sourced from the literature ). It was concluded that Australian soils leak more P than soils of similar fertility in the USA, UK and New Zealand, although it was beyond the scope of the thesis to make more detailed comparisons between Australian and overseas soils. The accumulation and mobilisation of P in two soils used for intensive pasture production in Australia were investigated. In intensive pasture systems P accumulated in the shallowest zones of the soil and principally as inorganic P. The concentrations of labile P were 3 - 5 times higher in the top 0.01 m than in the top 0.1 m. Using a simple model, it was estimated that only the top several mm of soil influence runoff P concentrations. The dominant form of P in runoff was shown to be orthophosphate although in low to moderate fertility soils, dissolved organic P can constitute a substantial proportion of the P in runoff. These results confirm the need to reduce the pool of P available for mobilisation in the immediate topsoil in order to reduce runoff P concentrations. Because P is stratified, it was hypothesised that one method to reduce the pool of P available for mobilisation is to de - stratify the soil ( i.e. mix the topsoil ). The effect of this technique on runoff P concentrations was investigated in laboratory and rainfall simulation experiments. These experiments revealed that reductions in runoff P concentrations between 45 and 70 % can be achieved by de - stratification of soils under permanent pastures. It was hypothesised that the benefits of de - stratification could be maximised using a combination of information relating to catchment hydrology and the spatial distribution of soil P and that this would result in large reductions in P exports with a relatively small degree of inconvenience to land managers. Given the limited opportunities identified in previous research to reduce P exports in runoff, the strategic utilisation of de - stratification is a potentially important option in water quality management for the dairy industry and warrants further investigation.Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2006.
29
Dougherty, Warwick John. "The mobilisation of soil phosphorus in surface runoff from intensively managed pastures in South-East Australia". Thesis, 2006. http://hdl.handle.net/2440/37852.
Testo completoAbstract (sommario):
The application of substantial quantities of phosphorus (P) has been required to increase productivity on many Australian soils. Unfortunately, these applications have often resulted in increased concentrations of P in surface runoff that contributes to excessive algal growth in surface waters and consequently a decline in their quality. The concentrations of P in runoff from intensively managed pastures are often high (1-5 mg/L) and typically at least an order of magnitude higher than water quality targets. Although a substantial amount of research has been devoted to the problem of P accumulation and mobilisation in arable systems ( in which P is typically mobilised by the action of raindrop impact and subsequently transported in particulate form ), there has been substantially less research in intensively managed pasture systems. Consequently, there is a paucity of knowledge concerning the fundamental processes and factors responsible for P in runoff from these systems and a dearth of truly effective remedial strategies.
In this thesis, the accumulation of P in soil under intensively managed pastures used for dairying and the processes responsible for its mobilisation in surface runoff were investigated. This research was undertaken at two research sites in South - east Australia, i.e. Camden in New South Wales and Flaxley in South Australia.
A number of factors relating to scale and hydrology may influence the processes of P
mobilisation and its concentration in runoff. A comparison was made of the forms and concentrations of P in runoff between a typical rainfall simulation methodology and large runoff plots. The effect of rainfall intensity on the forms and concentrations of P was also investigated. The concentrations of P in runoff from small - scale, high - intensity rainfall simulations were on average 33 % lower than those from large plots ( approximating hillslopes ) although the processes of mobilisation ( as evidenced by runoff P forms ) were similar. Increasing rainfall intensity resulted in decreasing P concentrations, but similar forms of P. It was hypothesised that changes in hydrological characteristics ( residence time and depth of runoff ) were responsible for the differences in the P concentrations. A model of P mobilisation ( incorporating hydrological and P - release characteristics ) was developed and shown to successfully predict runoff P concentrations under a range of rainfall intensities. These findings and the subsequent model were used in the successful modelling of landscape scale nutrient exports based on rainfall simulation data as part of a separate, but complementary project.
There is anecdotal evidence to suggest that Australian soils are relatively ' leaky ' in terms of P in runoff compared to soils overseas. Consequently, comparisons of the labile soil P characteristics and soil P - runoff P relationships were made between Australian soils and soils of similar fertility from the USA, UK and New Zealand ( using both experimental data and data sourced from the literature ). It was concluded that Australian soils leak more P than soils of similar fertility in the USA, UK and New Zealand, although it was beyond the scope of the thesis to make more detailed comparisons between Australian and overseas soils.
The accumulation and mobilisation of P in two soils used for intensive pasture production in Australia were investigated. In intensive pasture systems P accumulated in the shallowest zones of the soil and principally as inorganic P. The concentrations of labile P were 3 - 5 times higher in the top 0.01 m than in the top 0.1 m. Using a simple model, it was estimated that only the top several mm of soil influence runoff P concentrations. The dominant form of P in runoff was shown to be orthophosphate although in low to moderate fertility soils, dissolved organic P can constitute a substantial proportion of the P in runoff. These results confirm the need to reduce the pool of P available for mobilisation in the immediate topsoil in order to reduce runoff P concentrations.
Because P is stratified, it was hypothesised that one method to reduce the pool of P available for mobilisation is to de - stratify the soil ( i.e. mix the topsoil ). The effect of this technique on runoff P concentrations was investigated in laboratory and rainfall simulation experiments. These experiments revealed that reductions in runoff P concentrations between 45 and 70 % can be achieved by de - stratification of soils under permanent pastures. It was hypothesised that the benefits of de - stratification could be maximised using a combination of information relating to catchment hydrology and the spatial distribution of soil P and that this would result in large reductions in P exports with a relatively small degree of inconvenience to land managers. Given the limited opportunities identified in previous research to reduce P exports in runoff, the strategic utilisation of de - stratification is a potentially important option in water quality management for the dairy industry and warrants further investigation.Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2006.
30
Johnston, William H. "The role of Eragrostis curvula (Schrad.) Nees. complex in temperate pastures in southeastern Australia". Thesis, 2003. http://handle.uws.edu.au:8081/1959.7/29.
Testo completoAbstract (sommario):
This thesis examines the hypothesis that, in southern New South Wales and northeast Victoria, Australia, palatable taxa of E. curvula offer advantages that complement those of the species that are traditionally sown in temperate pastures in a landscape context.This hypothesis was based on a review of literature showing that, prior to European settlement, the vegetation, the landscape and the climate were broadly in balance, and the wateruse pattern of the vegetation of southeastern Australia resulted in water being used more-or-less completely by the end of summer. This maximised the capacity of the soil to take up and store water during autumn and winter.Three grazing experiments and one spaced-plant species evaluation study were used to assess the role of summer-growing, C4 Eragrostis curvula in pastures in the temperate zone of southeastern Australia.Issues relating to pasture production and the productivity of wool-growing sheep were investigated. Factors affecting the sustainability of the pastures and their potential on and off site impacts were emphasised.Modelling was used to explore issues of water use, arising from the grazing experiments. It is concluded that the persistence, production, water use patterns, and the adaptability of palatable varieties of E. curvula make it a useful and complementary addition to the range of species that are currently available for use as sown pastures in southern Australia.
31
Dalby, Paul Reginald. "Competition between earthworms in high rainfall pastures in the Mt. Lofty Ranges, South Australia / Paul Reginald Dalby". Thesis, 1996. http://hdl.handle.net/2440/18758.
Testo completoAbstract (sommario):
Copy of author's previously published work inserted.Bibliography: leaves 261-306.
xxix, 308 leaves : ill. (some col.), maps ; 30 cm.
The objectives of the project were: i. to determine whether there are competitive interactions between Aporrectodea trapezoides and A. caliginosa and A. rosea.--ii. to investigate compeditive interactions between A. calignosa, Microscolex dubius and A. trapezoides.--iii . to determine the likely impact of A. longa on soil fauna, especially the native earthworm, Gemascolex lateralis, in native ecosystems.
Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1996
32
Armstrong, Helen M. "Effects of rabbits on the vegetation of an arid zone national park". Phd thesis, 1988. http://hdl.handle.net/1885/142801.
Testo completo
33
McCloy, K. R. (Keith R. ). "Development and evaluation of a remote sensing algorithm suitable for mapping environments containing significant spatial variability : with particular reference to pastures". 1987. http://web4.library.adelaide.edu.au/theses/09PH/09phm127.pdf.
Testo completo
34
McCloy, Keith R. "Development and evaluation of a remote sensing algorithm suitable for mapping environments containing significant spatial variability : with particular reference to pastures / by Keith R. McCloy". 1987. http://hdl.handle.net/2440/18902.
Testo completoAbstract (sommario):
Includes bibliographical references (leaves 176-179)xiii, 202 leaves : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, 1989
35
McCloy, Keith R. "Development and evaluation of a remote sensing algorithm suitable for mapping environments containing significant spatial variability : with particular reference to pastures / by Keith R. McCloy". Thesis, 1987. http://hdl.handle.net/2440/18902.
Testo completo
36
Barnett, Kirk. "Hidden herbivory, precarious precipitation and punished pastures : Australia's grasslands under root herbivory and altered rainfall". Thesis, 2016. http://hdl.handle.net/1959.7/uws:43134.
Testo completoAbstract (sommario):
Climate change researchers are predicting more variable rainfall in the coming decades. This is important for grasslands because they are highly responsive to inter- and intrannual rainfall patterns. At the same time, root damage from soil-dwelling arthropods has the potential to exacerbate, or in some cases reverse, the effects of rainfall variability in grassland. Plant community changes are likely to affect aboveground arthropod communities as a result.
Recent literature on the effects of rainfall on grassland ecosystems and soil-dwelling invertebrates are synthesized in chapters one and two, respectively. While reduced rainfall amounts are expected to result in lower soil water content, the effects of variable rainfall are unclear and depend highly on grassland type. Plant functional types within grassland communities are likely to play a role in determining these responses and will interact with above- and belowground arthropod communities. Soil-dwelling insects are known in Australia for their high densities during pest outbreaks, especially scarab larva. While these organisms are affected by soil water content, they are predicted to be less vulnerable than organisms aboveground due to physiological and behavioural adaptations. Therefore, they are likely to damage plant roots in grassland ecosystems, even under fluctuating soil moisture.
In this thesis I aimed to better understand the responses of grassland organisms that were subjected to rainfall regimes predicted under climate change for SE Australia. I also sought to determine if root damage by local scarab beetles could change the productivity and diversity of the aforementioned grassland in response to rainfall alterations. As such, I attempted to answer the following questions: 1) how will varying water regimes and root damage impact the performance of grasslands at the individual species level; 2) how will changing the amount and frequency of rainfall affect soil water content and how soil water content changes impact grassland plant and invertebrate communities when coupled with increased root herbivore densities and; how are above- and belowground plant community traits relevant to arthropod herbivore performance affected by both extreme rainfall and increased root herbivore density . I hypothesized that rainfall alterations would lead to shifts in grassland productivity and composition, on both the individual and community level. Additionally, root damage would exacerbate the effects of water stress on grassland communities. Finally, grassland community plant traits (e.g. nutrient density, diversity, apparency, etc.) were hypothesized to shift in response to the most extreme forms of water limitation, affecting aboveground herbivore performance.
In Chapter three, I examined plant growth, phenology, productivity and physiology to evaluate the effects of rainfall regime and root damage on plant performance. I found that simulated rainfall reduction had a much larger impact on plant productivity than root damage. However, the magnitude of reduction in biomass due to water stress was highly dependent on grass species. Water stress and larval activity interacted leading to increased biomass root:shoot ratios for two grass species. Plant growth and flowering time was affected by water treatments, but not larval activity. I did find, however, strong trends in the concentration of silicon in plant tissue in response to water stress.
In Chapter four I measured the responses of grassland plots under altered rainfall and increased root herbivore densities. I found rainfall had a much stronger influence on grassland productivity and plant community composition than increased root herbivore densities. Where the plant community was affected by rainfall, there was evidence of plant-mediated effects on aboveground invertebrate community structure.
In Chapter 5 I use the same experimental plots as above but with a focus on plant trait changes in response to extreme rainfall, as well as the other rainfall scenarios. I found that extreme drought can have severe and immediate effects on plant communities in terms of apparency and plant traits that are potentially important for aboveground herbivore performance. Interactions with root herbivory treatments are mixed; in some cases it had a stimulatory effect on plant traits and in others a depressive effect. Plant traits also shift with rainfall regime and, overall, summer drought and reduced frequency rainfall elicited plant trait responses counter to arthropod herbivore performance. Increased rainfall did not have as much of an effect as expected, possibly because of the high sand content and, thus, porosity of the soil at the site.
The effects of watering regimes in this thesis were expected to be measurable and to interact with damage caused by root feeders. However, for the most part reduced amount and frequency watering regimes resulted in very similar response levels and root damage effects tended to be negligible. At the community level, responses of root damage and altered water regimes were even less pronounced and almost exclusively interacted in ambient (control) water treatments. It can therefore be assumed that plants use a stress hierarchy when responding to both stressors; here, available soil water seems to be at the top and moderate root damage a lesser concern. This work brings the field one step closer to understanding the complex relationships above- and belowground that are expected to shift in grasslands under climate change. Researchers should strive to understand ecological interactions, no matter how difficult they are to elucidate.
37
Pitman, Ashleigh. "The influence of drains and perennial pastures on soil-water-nutrient dynamics of texture contrast soils down a toposequence at Keyneton, South Australia/ Ashleigh Pitman". 2005. http://hdl.handle.net/2440/22263.
Testo completoAbstract (sommario):
"May 2005"Bibliography: leaves 202-220.
viii, 220 leaves : ill. (some col.), maps (chiefly col.), plates, photographs (chiefly col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Dept. of Agronomy and Farming Systems, 2005
38
Pitman, Ashleigh. "The influence of drains and perennial pastures on soil-water-nutrient dynamics of texture contrast soils down a toposequence at Keyneton, South Australia/ Ashleigh Pitman". Thesis, 2005. http://hdl.handle.net/2440/22263.
Testo completoAbstract (sommario):
"May 2005"Bibliography: leaves 202-220.
viii, 220 leaves : ill. (some col.), maps (chiefly col.), plates, photographs (chiefly col.) ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Dept. of Agronomy and Farming Systems, 2005
39
Dorrough, Josh. "The impact of grazing and exotic invasion on the persistence of native grassland". Phd thesis, 2001. http://hdl.handle.net/1885/148807.
Testo completo
40
Ru, Ying Jun. "The influence of cultivar variation on the potential productivity of swards of subterranean clover when utilised by grazing animals / by Yingjun Ru". 1996. http://hdl.handle.net/2440/18931.
Testo completoAbstract (sommario):
Bibliography: leaves 144-163.xv, 163 leaves : ill. ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
This thesis examines genetic variation in growth rate and growth form among subterranean clover cultivars in winter. The effect of plant density and sowing time on growth rate and sward structure of subterranean clover in winter and the impact of grazing intensity on morphology and nutritive value of subterranean clover is studied. It explores also genetic variation in the nutritive value of subterranean clover.
Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 1997
41
Roberts, Craig Penny. "Development of a novel crop-pasture system for mixed farms in the higher rainfall zone of southern Australia". Thesis, 2011. http://hdl.handle.net/2440/72860.
Testo completoAbstract (sommario):
The use of annual-based pasture and/or annual crops is now common practice in the higher rainfall regions of southern Australia where livestock grazing is the traditional practice. The lower water use of these annual-based systems, compared with systems based on perennial pastures, exacerbates issues of waterlogging, rising watertables and salinity in these regions. For environmental reasons farming systems used in the higher rainfall regions should target the use of more perennials in the landscape, but this should not be done at the expense of farm productivity or profitability. Intercropping, where the pasture component of the system is a perennial species, may provide the opportunity to maintain or improve farm productivity whilst delivering favourable environmental outcomes. A study of crop/perennial pasture intercrops is the core investigation undertaken in this thesis. Perennial pasture species lucerne (Medicago sativa) and chicory (Cichorium intybus) were established and maintained for three seasons with annually sown (2006-08 seasons) crop species (wheat (Triticum aestivum), lupin (Lupinus angustifolius) and canola (Brassica napus)), in a double skip row arrangement. These intercrops were compared for production, resource use and farm productivity with the individual crops and pastures grown as monocultures. Yields of grain crops were reduced when grown in intercrop with lucerne and chicory. Grain yield reductions ranged from 0-46% for wheat, 45-74% for lupins and 8-83% for canola. Pasture dry matter was also reduced when intercropped, ranging from 0-78% for lucerne and 19-78% for chicory. Despite the reduction in crop and pasture production, the Land Equivalent Ratio (LER) (used as a measure of the productivity of the intercropping system) ranged from 0.71-1.66, with all intercrop combinations over-yielding (LER 1.01 -1.66) in favourable growing seasons. With soil moisture becoming limited during September/October (measured using Time Domain Reflectometry), the grain yield components of wheat heads/m² , number of lupin branches/plant, pod number/plant and pasture dry matter were reduced by competition. Lucerne intercrops gave higher yield penalties to the companion species, attributed to greater competition for soil moisture between the component species. Higher soil moisture (9-25mm) for monoculture chicory, compared to monoculture lucerne, indicates chicory growing in intercrop was not likely to compete as strongly for water as lucerne. Plant height and Leaf Area Index (LAI) measurements were taken to assess light capture and showed minimal incidence of light competition in the intercrops. As a result, it was concluded that competition for water was the main resource competition responsible for yield reductions in intercrops. The Agricultural Production System Simulator (APSIM) model was used to try to assess longer-term intercrop productivity. The model was satisfactory in simulating monoculture crop production; however there was poor agreement for monoculture lucerne production and this subsequently affected the modelled agreement with intercrop production. Notwithstanding these discrepancies, some of the modelled data and extrapolated data were used to produce a medium-term productivity dataset for economic analysis. Economically, the intercrops were found to have higher gross margin returns than monoculture pastures, and lower gross margins of $39-55/ha when compared to monoculture crops. Despite yield reductions in the intercrop components, intercropping increased productivity compared to growing the components as monoculture stands. It also provided an environmental benefit of retaining perennial pastures in the system, and produced comparable economic returns to the growing of monocultures stands/swards.Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2011
42
(9834095), Deepak Sharma Paudel. "Grain quality of rice (Oryza sativa L.) genotypes grown under aerobic and rainfed production environments in Queensland, Australia". Thesis, 2018. https://figshare.com/articles/thesis/Grain_quality_of_rice_Oryza_sativa_L_genotypes_grown_under_aerobic_and_rainfed_production_environments_in_Queensland_Australia/13445642.
Testo completoAbstract (sommario):
The Australian rice industry faces tremendous pressure for incremental increase in water use efficiency. Rainfed (RF) rice production could provide opportunities for diversifying the options for the rice industry to address the issue of water shortage. Rice varieties for RF production need to be developed to extend the rice industry to Australian wet-tropical regions. Achieving economic yields and matching grain quality to market standards are some of the challenges for RF rice production. Thirteen RF rice genotypes obtained from Australian Agricultural Technologies Limited (AAT) were evaluated during 2013 – 2015 in central and north Queensland locations as RF and supplementary/strategic irrigation (SI) crops, and were assessed for their yield potentials and grain quality performances.
The results from varietal trials under RF and SI showed large genetic variation, primarily associated with grain types (GT), for yield and grain quality attributes. The long grain (LG) types recorded significantly greater (6.7 fold) yield response to SI (3.16 vs 0.47 t/ha) compared to the medium grain (MG) type varieties (1.8 fold yield in SI) (4.37 vs 2.49 t/ha). The RF yields under the drier tropical environment of Alton Downs (AD) were limited by a short growing season and low rainfall which impacted on late maturing LG type indica varieties. However, greater yield was recorded for early maturing, MG type japonica varieties. The effect of SI on grain quality was not as strong as the effects on the yields. Among the milling characteristics millout, was significantly greater for LG compared to MG type (0.58 vs 0.47) under the SI. Among the chemical characteristics, the SI rice showed greater gelatinisation and pasting temperature compared to RF rice, particularly in the second year, due to earlier planting, therefore, LG type varieties escaped low temperature stress. The effects of SI on physical, cooking and nutritional characteristics were not significantly. Given the short window of the warm, wet season (January – May) at AD, the performance of LG types was significantly favoured by SI. The LG type were generally late maturing, and therefore, flowering and grain filling coincided with cold spells, particularly for late planted crops. Hence, a RF cropping option at AD is favourable for short duration MG type varieties.
In the varietal evaluations under RF production over multiple seasons of three years, RF yield was 1.38 – 1.43 t/ha. The overall yield of MG type was significantly greater compared to LG type (2.49 vs 0.47 t/ha). In the first season (planting February 2013), none of the LG type produced yield; however, in the second and third season (planted in January and November), LG type varieties produced yields of 0.12 – 0.66 t/ha. These longer term yield data for LG types clearly demonstrated that the commercial harvest of LG as a rainfed crop in central Queensland could not be a viable option. Among the MG types the higher yielding varieties were AAT-4 and AAT-19 (2.92 t/ha), followed by AAT-6 and AAT-17. In spite of the low yield, the milling ratio/millout was significantly higher in LG types compared to MG varieties. The Year (Y) x Grain type (GT) x Variety (V) interaction for milling ratio was due to the fact that the varietal effect was significant in both grain types, as LG variety AAT-12 recorded the highest millout (~0.60), whereas MG variety AAT-4 maintained lowest mill out (0.40) in the first year. Similarly, chalkiness was significantly higher for MG compared to LG (14% vs 7%) types. The grain chemical characteristic measured as alkali spreading value was significantly greater for MG compared to the LG varieties (6.01 vs 1.60 score). The amylose content differed significantly due to YxGTxV interactions suggesting greater genotype x environmental effects. Amylose content was greater in year1 followed by year2 and year3, and was generally higher for LG compared to MG. However, the highest amylose containing LG varieties AAT-15 and AAT-16 in 2013 and 2014 showed significant reduction of amylose in 2015 but the amylose content of LG AAT-18 recorded consistently higher amylose (24%) in all 3 years. The gelatinisation temperature (GeT) of LG type lines was significantly greater than that of the MG types (74.2 °C vs 70.2 °C). In summary, the yield performance of LG type at AD was low, primarily governed by a smaller planting window for late maturing rice varieties. Some of the MG type varieties, e.g., AAT-4 recorded the highest but economically marginal yield, but the MG types suffered from poor grain quality associated with the lowest millout and higher chalkiness; both of these contributed negatively to marketable yield. Hence, a RF rice crop performance under a dry tropical environment with limited rain and a short planting window can be a significant limitation for development of the RF rice industry.
The AAT rice varietal evaluations in contrasting RF environments of AD (c. 593 mm rain) and wet tropical South Johnstone (SJ) (c. 876 mm rain) showed that paddy yield in the SJ was 2.4 times greater than at AD (4.66 vs 1.92 t/ha), and the yield difference between the LG and MG in the wet tropics was not significant (4.92 vs 4.36 t/ha), demonstrating the opportunity of commercial RF rice crops for both grain types. Significant effects of the growing environment were noted on grain quality parameters. Millout was consistent across the locations; however, a greater millout was recorded for LG compared to MG type (0.56 vs 0.50). Although greater chalkiness was recorded for MG compared to LG types at AD (27% vs 13%), no difference between GT for GeT was recorded at SJ. The GeT varied between 71.3 and 80.0 °C and differed due to GT x V interaction; the greatest GeT (80.2 °C) was recorded for AAT-4 at both locations. The amylose content is related to cooking and nutritional quality, but did not vary significantly due to V and locations. The effect of growing location was significant for cooking time, suggesting that grain from AD took longer to cook (42 vs 29 minutes). Nutrition characteristics, primarily the protein, nitrogen and sulphur concentrations of the grain were higher at SJ, irrespective of the GT compared to AD where the protein, nitrogen and sulphur concentration decreased in MG compared to LG varieties, showing significant L x GT interactions. Under the environment of SJ, the yield and grain quality of LG varieties were enhanced when compared to AD. The results showed that AAT RF rice varieties in SJ could produce a feasible crop, with acceptable level of milling recovery, and grain quality traits comparable to those of the commercially recommended varieties such as Topaz and Doongara in tropical Australian north Queensland.
43
(217363), Mei Li. "Genetic diversity, physiology and production of Chinese water chestnut (Eleocharis dulcis (Burm. f.) Trin. ex Henschel)". Thesis, 1998. https://figshare.com/articles/thesis/Genetic_diversity_physiology_and_production_of_Chinese_water_chestnut_Eleocharis_dulcis_Burm_f_Trin_ex_Henschel_/20010443.
Testo completoAbstract (sommario):
Chinese water chestnut (Eleocharis dulcis (Burm. f.) Trin. ex Henschel) is a new aquatic vegetable to Australia. Lack of research on this crop greatly limits the understanding of its production performance. Therefore, studies on several aspects of this crop were undertaken to provide a scientific basis for improvement in yield and quality.
Firstly, the genetic relationship of Chinese water chestnuts growing in Australia was assessed by using random amplified polymorphic DNAs (RAPDs). For the genetic
analysis of wild putative E. dulcis, three primers separated the samples from 9 out of 10 sites into two distinct groups: E. dulcis and E. sphacelata. In the genetic analysis of samples from cultivated E. dulcis plants, 96 RAPD markers generated by 14 primers separated the samples from Taiwan (var. Shu-Lin), Hangzhou, China (cv. Da Hong Bao), New South Wales, Australia (unknown variety) and the USA (unknown variety) from the rest of the samples from Australia. The remaining samples were too closely related (0.74-4.4% dissimilarity) to be differentiated.
Secondly, the possibility to extend availability of fresh Chinese water chestnut corms by physiological manipulation (photoperiod control) was evaluated in four
photoperiod experiments. When measured, above -ground growth and dry matter production of the whole plants were not significantly affected by photoperiods (8-24 h). However, corm formation was strongly retarded by long days and promoted by the photoperiod which was shorter than a critical value. Under shorter days, significantly more dry matter was shifted towards corms as well as rhizomes, an
effect that became more pronounced as the period of treatment was lengthened.
Thirdly, Chinese water chestnut production in relation to harvest date and cold storage of 'seed' corms was investigated in two experiments. In the first experiment,
March -planted plants were harvested from July to September. Mature corms from each harvest were subsequently stored at 4°C. In terms of corm formation and
maturation as well as soluble sugar concentration in mature corms, the harvests in August were more favorable. After storage at 4°C for 86 d (harvest on 24 September)
to 159 d (harvest on 15 July), no sign of rot nor flesh deterioration was observed. Loss of fresh weight ranged from 0.46% to 6% with the lower value associated with
the shorter storage duration. Corm germination was also favored by shorter storage period. The highest values for the number of sprouts and stems per viable corm and
the length of the longest stem per viable corm were obtained from the harvests on 29 July (139 d storage), 13 August (130 d storage) and 27 August (116 d storage)
respectively. In the second experiment, corms harvested on different dates over the period July to November were stored at 4°C for four different periods prior to planting. Both harvest date and cold -storage duration exhibited significant influence on soluble solid content (°Brix) with the highest values for the first harvest and no cold storage, although the average °Brix value was low for all treatments. Harvest
date and cold -storage duration also showed significant effects on corm sprouting performance evaluated as the number of sprouts and stems, and the length of the
longest stem per viable corm. Average yield per plant showed little difference across `seed' corm harvest dates with the exception of the last. The fresh weight of individual corms was significantly affected by 'seed' corm harvest date but not by storage duration.
Fourthly, the possibility of Chinese water chestnut in vitro culture was investigated with several different explants and culture media. Among all the explants examined, only young rhizome nodes and tips, dormant buds and corm skin with bud scars (buds removed) responded to in vitro culture by the production of shoots or shoot clusters. Root initiation was readily stimulated in the derived microshoots. The test
tube plantlets were successfully transferred to the screenhouse, and their subsequent performance compared favorably with that of corm -derived plants.
Lastly, a putative Chinese water chestnut disease, tip yellowing and brown stem lesions, which was observed in the greenhouse and in the field, was studied. As no
corresponding symptoms showed up when healthy plants were inoculated with spores derived from the isolates obtained from affected tissue, a nutritional disorder,
perhaps potassium deficiency, was therefore suggested to have been responsible for the symptoms.
44
Langworthy, AD. "Mitigating the detrimental effects of hot and dry summers on the south-eastern Australian dairy feedbase". Thesis, 2019. https://eprints.utas.edu.au/31466/1/Langworthy_whole_thesis.pdf.
Testo completoAbstract (sommario):
This thesis investigated strategies for mitigating detrimental effects of hot and dry summers (i.e. supraoptimal temperatures and soil water deficit stress) on home-grown feed production in south-eastern Australian dairying regions. Strategies included incorporating alternative species into the feed-base and modifying aspects of feed-base management. Field research was conducted in north-west Tasmania, where summer conditions are forecast to become hotter during the 21st century, challenging the existing perennial ryegrass (Lolium perenne L.) feed-base.
A glasshouse study (Chapter 3) identified summer-active temperate perennial forages more tolerant than perennial ryegrass of the combined stress of supraoptimal temperatures and water deficit. These species were examined as they are known to possess key attributes underpinning perennial ryegrass’ popularity (i.e. they are perennial, grazeable, and of high nutritive value). Species exhibiting greater tolerance than perennial ryegrass included chicory (Cichorium intybus L.), and to a lesser extent lucerne (Medicago sativa L.), plantain (Plantago lanceolata L.), and tall fescue (Festuca arundinacea Schreb.). Tolerance did not pertain to growth occurring when exposed to the combination of stresses, but was a result of these plants capacity to survive and resume growth when more favourable conditions returned.
An accompanying field experiment (Chapter 6) tested the potential of chicory and tall fescue to increase summer-autumn growth beyond that achievable by perennial ryegrass in north-west Tasmania. Under both irrigated and rain-fed conditions, chicory did not increase summer-autumn growth beyond that achieved by perennial ryegrass. In contrast, irrigated tall fescue achieved a similar total yield to comparably managed perennial ryegrass over a 15-month period, and in the second of two growing seasons, 10% greater summer-autumn yields. The potential role of tall fescue in north-west Tasmania was further demonstrated by the species high marginal irrigation water-use index (1.6-2.7 t DM/ML). Field research showed rain-fed chicory and second year tall fescue swards experienced less extreme crown (plant-soil interface) temperatures than perennial ryegrass (Chapter 4). This feature may contribute to their superior growth in hotter summer environments than north-west Tasmania.
Field research confirmed the crown temperatures of these species can be manipulated by both stubble height (height of stubble above the soil surface post-defoliation) and irrigation management. Defoliating to shorter stubble heights (35 mm or 55 mm cf. 115 mm) elevated the upper distribution of crown temperature (75th and 90th percentiles) in subsequent regrowth cycles (Chapter 4). In the second of two summers, defoliating to shorter stubble heights increased the 90th percentile of crown temperature by an average of 4.2°C for perennial ryegrass, 3.6°C for tall fescue, and 1.8°C for chicory. Differences in crown temperatures may be partly attributed to the canopy base being less shaded when defoliated to shorter stubble heights (i.e. swards having lower leaf area indices). Despite experiencing these higher summer crown temperatures, each species achieved greater summer-autumn yields when defoliated to shorter stubble heights (Chapter 6). This is explained by north-west Tasmania’s cool temperate climate, limiting the extent and/or duration of supraoptimal crown temperatures.
Irrigation mitigated detrimental effects of supraoptimal temperature stress on growth and survival of all species examined in the glasshouse study (Chapter 3). Field research tested the role of irrigation frequency in mitigating the detrimental effects of supraoptimal temperature stress on perennial ryegrass pastures (Chapter 5). Addressing this research question necessitated the development of a novel outdoor warming system to reliably simulate heat wave conditions. The developed outdoor warming system was successfully deployed, with results showing irrigating at higher frequencies suppressed elevation of perennial ryegrass crown temperature under heaters. The median crown temperature differential between heated and unheated plots equalled 5.5°C, 6.5°C, and 7.0°C for swards irrigated every 2, 5, and 10 days respectively. Because soil water deficits never developed to an extent where transpiration was unduly constrained, irrigating more frequently did not mitigate the detrimental effects of applied heating on growth of perennial ryegrass.
These experiments have: (i) identified summer-active temperate perennial forages more tolerant than perennial ryegrass of the combined stress of supraoptimal temperatures and water deficit; (ii) found, in north-west Tasmania, irrigated tall fescue summer-autumn growth can exceed that achieved by comparably managed perennial ryegrass; (iii) shown, defoliating to higher stubble heights and irrigating more frequently maintains cooler crown temperatures; and (iv) developed a novel outdoor warming system for use in evaluating heat wave mitigation strategies. Identification of species more tolerant of hot and dry conditions, and management strategies that limit crown temperature elevation, are important steps in future-proofing north-west Tasmanian dairy farming systems against a warming climate. When interpreting results from field experiments, the influence of environment as a component of the genotype by environment by management interaction should not be ignored. In south-eastern Australian dairying regions warmer than north-west Tasmania, the application of management practices that maintain cooler crown temperatures may benefit temperate pasture production. This requires confirmation, with future research also required to evaluate the potential role of these management practices at a whole farm system level.
45
(9834818), Sachesh Silwal. "Comparative analysis of physiological and phenological traits of rice (Oryza sativa) under aerobic production systems in dry and wet tropics of Queensland, Australia". Thesis, 2017. https://figshare.com/articles/thesis/Comparative_analysis_of_physiological_and_phenological_traits_of_rice_Oryza_sativa_under_aerobic_production_systems_in_dry_and_wet_tropics_of_Queensland_Australia/13452425.
Testo completoAbstract (sommario):
Aerobic rice is becoming a more promising rice cultivation system due to increasing water scarcity for irrigation and occurrence of drought, especially in Australia. Rice cultivation on aerobic soil under rainfed conditions has shown potential for successful rice cultivation in tropical climate. Strategic irrigation during the critical growth period can help reduce the water demand on farm. Central Queensland has an annual rainfall of ca. 800 mm, and about 600 mm occurs during the wet season from December to March; whereas parts of the wet tropical north Queensland receive ca. 3000 mm annual rainfall, and about 1893 mm during the wet season from December to March. The study was carried out at Alton Downs, central Queensland (dry tropics) and South Johnstone, north Queensland (wet tropics) to investigate the phenological, physiological and agronomical responses of 13 different rice varieties with a view to identifying suitable varieties for dry land cultivation. The objectives were to assess rice varieties under i)
rainfed conditions in the wet and dry tropics, ii) rainfed conditions and strategic irrigation condition in the dry tropics, and to iii) identify the physiological, phenological and agronomical traits of rice adaptation under aerobic conditions in the dry and wet tropics. In the dry tropics, the strategic irrigation was provided by drip irrigation and was scheduled when the rice plants showed water deficit symptoms (corresponding to the refill point at 21 mm /100 mm soil water). The average yield of rice varieties under strategic irrigation was significantly higher and the variety best yield (AAT 4) produced up to 5.23 t/ha in the year 2015 under strategic irrigation. The average yield of varieties was increased from 1.5 times (AAT 4) to 16.8 times (AAT 15) with strategic irrigation, as compared to rainfed conditions. The average water productivity was increased by 100 % in 2014 and by 110.3 % in 2015 using strategic irrigation as compared to rainfed. The average water productivity was 0.24 t/ML (in 2014) and 0.61 t/ML (in 2015) under strategic irrigation, whereas it was 0.12 t/ML (in 2014) and 0.29 t/ML (in 2015) under rainfed conditions. The high yielding varieties were early flowering types, which escaped the terminal drought caused by lower rainfall during the flowering stage, whereas the late varieties such as AAT 10, AAT 11 and AAT 15 were among the highest yielders in the wet tropics under rainfed
conditions. The greater yield was associated with greater panicle fertility, leaf area index , higher photosynthetic rate and water use efficiency during flowering, and one of the high yielding varieties (AAT 3) had the highest photosynthetic rate during the grain filling period in both strategic irrigation and rainfed conditions. Root dry weight and root weight density in the top soil layer at 0–15 cm were found to be related to yield under
strategic irrigation, but the varietal characteristic of deep rooting was not correlated with yield. It is important to consider variations in flowering time, yield potential and drought patterns while developing varieties for aerobic conditions, as the drought reduced the panicle filling percentage to 1% under rainfed conditions.
The variety with most stable and consistent yield at Alton Downs was AAT 6, and had the lowest coefficient of variation across the years whereas the variety AAT 13 was found to be more responsive with better growing conditions at Alton Downs under rainfed conditions. The varieties when sown late, late flowering varieties were subjected to cold and terminal drought reducing the yield. AAT 6 and AAT 13 are both early flowering
varieties.
In the wet tropical environment, the crop received rainfall until harvesting time. The favourable physiological characteristic of high yielding varieties such as AAT 4 and AAT 6 in the dry tropics was greater water use efficiency, and the agronomic characteristics were higher panicle fertility, higher effective tillers per plant and grains per panicle. In the wet tropics (South Johnstone), the high yielding variety AAT 10 was characterised by
high harvest index, longest panicle length, higher effective tillers, higher panicle fertility and higher water use efficiency.
In South Johnstone, the days to flowering did not have any effect on the yield of varieties. The varieties those producing least yield under rainfed conditions at Alton Downs were among the highest yielders in South Johnstone. The high yielding varieties maintained greater effective tillers per plant, heavier 1000 grain weight, greater harvest index and fertility. Reliable soil moisture favoured photosynthetic rate and water use
efficiency and the associated larger flag leaf area contributed significantly to higher yields at wet tropical South Johnstone as compared to dry tropical Alton Downs.
Strategic irrigation in dry tropical environments could allow plants to cope with water stress caused by less rainfall during the grain filling period. Similar yield was achieved under strategic irrigation for late flowering varieties as under rainfed conditions for early flowering varieties. The varieties responded with an average increase of 11.87 kg/ha and
15.80 kg/ha with each additional 1 mm water application in 2014 and 2015 respectively. This shows that there is great commercial scope for strategic irrigation during water deficit periods, created by little or no rainfall, during critical crop growth periods for rice in the dry tropical environment of central Queensland.
In conclusion, this thesis increases the understanding the role of strategic irrigation and varietal characteristics for rice cultivation under the dry tropical agro‐ecological domain of central Queensland and the wet tropical conditions of north Queensland. Higher productivity of aerobic rice in dry tropical central Queensland is achieved with early flowering varieties, supported by strategic irrigation management during the water
shortage periods, with higher water use efficiency, greater number of spikelets, higher panicle fertility. In the wet tropical environment of northern Queensland, yield variation between varieties was not significantly affected by the days to flowering. However, further study for selection of varieties from more diverse germplasm for plant water
status and fertility, and different water management strategies under aerobic conditions needs, to be explored, to achieve the rice yield that can assure the commercial opportunity for rice production in the dry and wet tropical environments of Queensland, Australia.
46
(9875051), BR Weeden. "The commercial potential of sugar beet (Beta vulgaris) for sugar production in the Mareeba-Dimbulah Irrigation Area of North Queensland, Australia". Thesis, 2002. https://figshare.com/articles/thesis/The_commercial_potential_of_sugar_beet_Beta_vulgaris_for_sugar_production_in_the_Mareeba-Dimbulah_Irrigation_Area_of_North_Queensland_Australia/13424945.
Testo completoAbstract (sommario):
Sugarcane is a tropical plant grown for sugar production under a wide range of mainly warmer climates throughout the world whereas under temperate climates sugar beet is grown for sugar production. In Australia, sugarcane is grown predominantly in the tropical and subtropical regions of the east coast. Since 1996 there has been a rapid expansion of sugarcane production in the Mareeba-Dimbulah Irrigation Area (MDIA), which is part ofthe Atherton Tableland region, about 50 km inland from Cairns in north Queensland. The expansion has been due to declining sugar yields from sugarcane grown on the coast, several years of devastating storms and cyclones, population growth of Cairns taking up cane land for residential use and the availability of land and water in the MDIA. A major effect of this rapid expansion of sugarcane in the MDIA has been on the availability, supply and cost of irrigation water and the efficiency of water use has become an important issue for growers. This study investigates the potentia for sugar beet to be included into the cropping options of both established sugarcane farmers and other producers in the MDIA. As sugar beet has never been grown in the MDIA (and not commercially in Australia since the 1930 's) a number ofexperiments were conducted to provide yield information under local conditions. Variety trials studied the performance ofa number ofvarieties used in the main sugar beet growing areas ofthe UK, Europe and the USA. Results showed little difference in sugar yield between varieties which were in the range found under commercial production overseas (1012 t/ha). Nitrogen, irrigation and population experiments at two sites (Southedge and Walkamin) in1999 studied the effects of these inputs on sugar beet growth and yield. At Southedge the amount ofapplied nitrogen was having the greatest effect on root yield with 180 kg/ha N giving the highest sugar yield (13.9 t/ha) while the amount of irrigation and population level were less influential. At 180 kg/ha of N, water use efficiency (WUE) was 11.8 and 2.3 t/ML for root and sugar yield respectively in comparison to an estimated sugarcane WUE in the MDIA ofabout 8 and 1.5 t/MLfor cane and sugar yield. At Walkamin it was population level that was having the greatest effect with 100,000 plants/ha giving very high root yields (>100 t/ha) however the sucrose concentration was much less compared to Southedge and so sugar yields were not as high as may have been expected but still higher than Southedge (about 16 t/ha). Water use was about 50 % more on the heavier soil at Walkamin compared to Southedge with 100,000 plants/ha giving an average WUE of12.7 and 1.8 t/ML for root and sugar yield respectively. Growth analysis studies at Southedge showed that radiation would not be limiting to dry matter production, with the excess radiation increasing water use. At Walkamin dry matter production was related to plant population and a higher radiation use efficiency at Walkamin compared to Southedge. An economic study using simple gross margin analysis and yield data from the Southedge trial showed that sugar heet could be a profitable crop in the MDIA however at the current low world sugar prices commercial production is unlikely.
47
(12246268), Alan Andrew Duff. "Growth and development of onions in a subtropical environment". Thesis, 2004. https://figshare.com/articles/thesis/Growth_and_development_of_onions_in_a_subtropical_environment/19365128.
Testo completoAbstract (sommario):
Australia currently produces 210 000 tonnes of onions annually. The major production areas are in southern Australia where the predominant onion type is adapted to an intermediate long daylength. Queensland's annual production is stable at 10% (20 000 to 25 000 tonnes) of the national production. Ninety percent of the Queensland crop is grown in southern Queensland (Lockyer Valley and the Darling Downs). Small production areas can be found in central and tropical north Queensland. Consequently, onions in Queensland are grown under a predominantly subtropical environment. Crops are sown from late February to late June. An extensive range of cultivars is required to meet the changing environmental conditions that occur during this time period in order to achieve maximum economic crop yield. In the past, incorrect cultivar selection has resulted in high levels of doubling and bolting with a corresponding reduction in economic yield. This study conducted at Gallon Research Station in the Lockyer Valley investigated the growth and development of several cultivars currently available to growers in Queensland.
48
McLean, Michael John. "What do people think about GM pasture grasses? : an assessment of public attitudes to a new technology developed by the Molecular Plant Breeding CRC". Master's thesis, 2007. http://hdl.handle.net/1885/151610.
Testo completo
49
(12298370), Alison S. Jensen. "Redefining pachymetra root rot management strategies and cultivar resistance in commercial sugarcane fields". Thesis, 2020. https://figshare.com/articles/thesis/Redefining_pachymetra_root_rot_management_strategies_and_cultivar_resistance_in_commercial_sugarcane_fields/19426862.
Testo completoAbstract (sommario):
Pachymetra chaunorhiza is an important soilborne pathogen of sugarcane and is found only in Australia. Pachymetra root rot is managed primarily by growing resistant cultivars, which are chosen for planting based on oospore levels in the soil. This management strategy does not account for differences in virulence among Pachymetra populations, despite previous research demonstrating that two genetically distinct groups of Pachymetra occur, which may differ in pathogenicity. Higher than expected yield losses have been associated with high oospore levels under some cultivars with intermediate resistance to the pathogen. Increased virulence of Pachymetra towards specific cultivars, following long-term exposure to that cultivar, could explain these reports of high yield losses in intermediate cultivars. This research project aimed to deliver knowledge of the genetic and pathogenic variation among Pachymetra populations in different growing regions and following long-term exposure to different cultivars.
The level of genetic and pathogenic variation among Pachymetra populations and the factors contributing to pachymetra root rot were investigated in a series of field trials, glasshouse experiments and laboratory molecular analyses. Results from field experiments generally support the current guidelines used for Pachymetra management. No evidence was found to support the hypothesis that planting the same intermediate cultivar over multiple crop cycles could lead to higher than expected yield losses due to pachymetra root rot. Yield losses of 17 percent were associated with continual cropping of Q208A in a field trial near Bundaberg, in the southern Queensland sugarcane-growing region. A range of putative Pachymetra genes were identified which could play a role in pathogenicity. Collectively, the findings from this research supported the conclusion that two genetically distinct groups of Pachymetra occur in growing regions a) north of Townsville and b) south of Townsville, as previously reported. Three potential native hosts of Pachymetra were also identified, including Themeda australis and this finding supports the theory that lighter soil types are conducive to pachymetra root rot.
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(9808013), Joel Johnson. "Investigation of the phenolic and antioxidant content in Australian grains using traditional and non-invasive analytical techniques". Thesis, 2022. https://figshare.com/articles/thesis/Investigation_of_the_phenolic_and_antioxidant_content_in_Australian_grains_using_traditional_and_non-invasive_analytical_techniques/21514560.
Testo completoAbstract (sommario):
Recent years have seen the emergence of the concept of “functional foods”– where the value of food products is based on their health-benefiting properties in addition to their basic nutritional value. Globally, the functional food market is worth US $170 billion and is projected to grow at 7.5% p.a. over the next 10 years. In order to capitalise on this lucrative emerging market, producers and wholesalers need to demonstrate that their products contain high levels of these desirable compounds. This is typically assessed through time-consuming, expensive analytical techniques such as high-performance liquid chromatography (HPLC) or liquid chromatography-mass spectrometry (LC-MS). While these methods provide a high level of specificity and sensitivity, more rapid analytical techniques may be better suited to the routine, near-real-time analysis of large numbers of samples. Furthermore, there is currently a lack of basic context data on the typical levels of bioactive compounds that are found in many crops grown under Australian conditions, particularly for grain crops. This lack of context data makes it challenging to know whether a particular product would be considered high or low quality from a functional food perspective.
Consequently, the first major aim of this project was to profile the typical levels of bioactive compounds present in economically significant grain crops grown in Australia – specifically faba bean, wheat, mungbean and chickpea. The major focus was on phenolic compounds, as these possess high levels of antioxidant activity and are found in relatively high levels in grain crops. Furthermore, this class of compounds is associated with a wide range of health benefits, particularly for the prevention of cardiovascular disease.
Using spectrophotometric methods and HPLC analysis, moderate differences were found in the phenolic contents and antioxidant capacity of different varieties from each crop. This was particularly noted for the ten varieties of faba bean analysed, where there was a 121% difference in total phenolic content (TPC) between the varieties with the lowest and highest contents. This pulse also contained the highest total phenolic contents (258-571 mg GAE/100 g) and ferric reducing antioxidant potential (237-531 mg TE/100 g) of all crops investigated. The five mungbean varieties showed lower levels and more minor differences in phenolic content (79-105 mg GAE/100 g; 32% variation between varieties) and cupric reducing antioxidant capacity (498-584 mg TE/100 g; 17% variation), while the while the ferric reducing antioxidant potential did not differ significantly between varieties (14-20 mg TE/100 g). However, the content of numerous phenolic compounds (p-hydroxybenzoic acid, vanillic acid, caffeic acid, sinapic acid, trans-ferulic acid, cinnamic acid and vitexin) were significantly different between the mungbean varieties investigated. Similar observations were made for the chickpea samples, where there were moderate differences in total phenolic content (73-94 mg GAE/100 g; 29% variation) and ferric reducing antioxidant potential (25-40 mg TE/100 g; 62% variation) between varieties. Again, the content of most phenolic acids analysed by HPLC were significantly different between varieties. Although varietal differences were not examined for wheat, the TPC of the 65 samples was higher than mungbean and chickpea (130-180 mg GAE/100 g), while the ferric reducing antioxidant potential ranged from 14-64 mg TE/100 g.
In addition to the varietal differences, the impact of growing location and season on phenolic content and antioxidant capacity were investigated in faba bean. Although these variables had no effect on the total phenolic content, the growing location did alter the levels of several individual phenolic compounds (protocatechuic, vanillic and chlorogenic acids, as well as the flavonoids vitexin and rutin).
The second major aim of this project was to investigate the prospect of infrared spectroscopy as a rapid technique for the prediction of phenolic content and antioxidant capacity in Australian grain crops. Promising results were found for the estimation of total phenolic content and antioxidant capacity in faba bean and wheat flour, particularly using near-infrared spectroscopy. The NIR model for TPC showed an R2test of 0.66 and RMSEP of 76 mg GAE/100 g when applied to faba bean, and an R2test of 0.86 and RMSEP of 4 mg GAE/100 g in wheat. However, infrared spectroscopy was unable to predict the concentrations of these analytes in mungbean or chickpea flour. This may be due to additional matrix constituents obscuring the analyte signals in the infrared region, or a consequence of the lower phenolic/antioxidant contents in these crops.
Nevertheless, the overall results suggest that infrared spectroscopy could be used for the estimation of total phenolic content or antioxidant capacity (i.e., prediction of high or low contents) in certain grain crops. This technique could potentially be applied for the routine screening of bioactive constituents, helping Australian producers to capitalise on the growing domestic and international functional food markets. Monitoring bioactive compound levels in Australian grain – either through traditional or non-invasive analytical techniques – could provide an additional level of quality assurance for producers of functional food crops and help maintain Australia’s global recognition as a producer of high-quality food.