School of Agriculture, Food and Ecosystem Sciences - Theses
Permanent URI for this collection
Search Results
1 - 8 of 8
-
ItemEffects of adding nutrients on soil chemistry and tree growth in native Eucalyptus forests of south-eastern Australia( 2007)The decreasing area available for timber extraction in south-eastern Australia, due largely to social pressure to reserve greater areas of forest, has led to the consideration of fertiliser-application to increase wood output from the remaining available forest. Potentially deleterious effects of fertilising on water quality must be assessed before implementation on a wide scale. This is in accordance with relevant forest management policies. This study examined the effects of applying fertilisers containing nitrogen and phosphorus, on soil and soil-water chemistry in two pole-sized stands of mixed Eucalyptus spp in the Wombat Forest, in the Midlands Forest Management Area, Victoria, Australia. The findings are synthesised and discussed in relation to management of regenerating mixed-eucalypt forests in south-eastern Australia. Fertiliser treatments were none (R); 400 kg N ha-1 as ammonium-sulphate (N); or 400 kg ha-1 plus 202 kg P ha-1 as triple superphosphate coated with 10% sulphur (NP). It was calculated that incidental additions of S were 1371 kg ha -1 (N treatments), and 1696 kg ha-1 (NP treatments). It was expected that P would be principally adsorbed on soil surfaces; N immobilised in the soil organic pool and that metallic cations would enter the soil solution to varying degrees. Fertiliser-addition increased both plot-basal-area (BA) growth and the rate of stand self-thinning. In 3.8 years, BA in reference (R) plots at two sites increased by 7.3% and 23.4%. Where N alone was added, BA increased by 14.2% and 27.1%, while in NP plots BA increased by 17.1% and 42.7% respectively. Mortality was 9% in untreated plots compared to 14% in NP plots. Estimated increases in biomass growth equated to additional above-ground nutrient accumulation of 0.4 to 1.5 kg ha-1 of P, and 5.5 to 20.8 kg ha-1 of N. This represented only 0.2 to 0.7% of added P, and 1.4 to 5.2% of added N. Soil solution was extracted from 10 and 50 cm with porous-ceramic-cup tension-lysimeters (-0.6 kPa). Concentrations of P and N were low both before and after adding fertiliser. Across all treatments the maximum median PO43- concentration in soil-water at 50 cm was 0.12 ppm (mean 0.28 ppm). Typically PO43- concentrations were not higher than 0.03 ppm. The 400 kg ha-1 of added N was rapidly immobilised in the soil organic pool. The greatest mean NH4' concentration from a single sampling occasion was 1.1 ppm. The mean NO3 concentration at 50 cm was never higher than 0.26 ppm. After adding N in fertiliser the proportion of NO3- relative to NH4* in soil-water increased and was correlated with decreasing soil-water pH. Less than 1% of added P and N was recovered from soil solution at 50 cm. The largest pool of added P recovered was PO43- adsorbed to soil between 0 and 20 cm, due to the soil adsorption capacity being well in excess of the applied 202 kg P ha-1. Phosphate desorption using sequential extractions with a mild acid extractant (0.3M NH4F, 0.1M HCI) recovered between 25% and 116% of added P. Differences were attributed to both the amount of P added and the effect of time since treatment at different sites. Soil disturbance during sampler installation was found to be more likely to raise soil-water P concentrations at 50 cm than would adding up to 202 kg P ha-1. Among the ions in solution. SO42- and CI' were the dominant anions while Cat+ dominated the cation chemistry. In untreated forest 5042- in soil-water ranged from 7.7 to 16.0 ppm at 10 cm and 7.9 to 12.2 ppm at 50 cm. In fertilised plots up to 100.5 ppm SO42 was measured in soil-water at 50 cm depth. In the N treatment at 50 cm, SO42- in soil-water accounted for 9.4 % of applied S. compared to 14.0 % in NP. In untreated forest, soil-water Cl- and SO42- accounted for over 98% of the total soil-water anions, in roughly equal proportions at 10 cm, and CI- slightly higher at 50 cm. Following fertiliser-application soil-water pH at 10 cm fell from 6.3 in R to as low as 4.81 (N) and 4.45 (NP). At 50 cm pH never dropped below 6 and there were no visible departures from reference concentrations. Relative activities of K+ and Mg2+ in solution increased with decreasing pH, indicating increased leaching potential. Sulphate in soil-water increased total anion charge further in NP than in N. Total charge (cmolc L-1) for cations followed anions. A slight deficit in anion charge was likely due to the unquantified contribution of organic anions. These results confirm that despite the quantity of fertilisers added in this trial being double likely operational quantities, the forest and associated soils had the capacity to retain these nutrients through a variety of processes. The study validates the environmental sustainability of proposed intensive management practices including fertiliser-application in this forest type. It also emphasises the importance of understanding fundamental forest nutrient cycling processes when aiming to carry out intensive forest management practices in an environmentally sensitive manner.
-
Item
-
Item
-
ItemAn investigation of environmental conditions experienced during the life of high value wood components and products( 2004)The purpose of this project was to collate data on Australian wood products' exports as well as the environmental conditions that these products are exposed to during manufacture, transportation and service. These data are essential for understanding the potential for wood components to `move' in response to periods of drier or more humid conditions than those at the time of manufacture. The knowledge generated will contribute to a subsequent project, whereby a user-friendly tool will be developed to enable for the design and production of appropriate components, joints, adhesives, coatings, and packaging systems that will ensure superior performance of Australian wood products throughout a wide range of climatic conditions. Wood, a hygroscopic material, will undergo changing moisture contents, fluctuating with changes in atmospheric conditions. As a consequence of these changes in moisture content, wood will swell or shrink. For high-value products, these changes can be detrimental to the utility of the product, for example panels can warp, drawers and doors can jam, and glued components can delaminate. Despite the common occurrence of product degrade or failure due to exposure to changing atmospheric conditions, very little effort has been undertaken to quantify the range of expected conditions for Australian exports. Australian forest industries have a long history of export trade in a wide range of products, from woodchips and sandalwood, through to high-value manufactured commodities such as outdoor furniture and assorted flooring products. Current export markets for high-value wood products were found to be predominantly northern hemisphere countries, including United States of America, China (including Hong Kong), Korea, Japan, Europe (including the United Kingdom) and the Middle East. Other regions importing Australian high-value wood products were south-east Asia (Philippines, Indonesia, Thailand and Malaysia), New Zealand and South Africa. A survey was undertaken to determine the range of value-added products currently exported, and it was found that high volumes of flooring, decking, outdoor furniture and kiln-dried boards for furniture and pre-finished flooring products account for the majority of our value-added export effort. There are currently only minor volumes of assembled indoor furniture suites exported from Australia. Wood fibre panels such as plywood, particleboard and medium density fibreboard were outside the scope of this project due to the in-built stability of these products and only solid wood products were considered. Data generated from the survey included the range of timber species used in the manufacture of export products, sawn orientation and typical section sizes used in components. Results from this work showed that the major timbers are: the ash-type eucalypts from south-eastern Australia; jarrah from Western Australia; spotted gum, hoop pine, white cypress, imported kwila, blackbutt, brush box and Sydney blue gum from New South Wales and Queensland. Environmental conditions, especially the combined effect of temperature and relative humidity in microclimates as determined during this research project, can fluctuate extensively during transport from one location to the next. Equilibrium moisture contents (EMC) as low as 5% and as high as 20% were experienced during the shipping of wood products. In addition, the conditions at the place of manufacture (often 10 to 12% EMC) may be vastly different to the environment where the wood products are ultimately placed in service. The in-service conditions for many of our export destinations are between 6 to 9% EMC. This range of conditions, from manufacturing through transportation and in-service, can potentially create problems, due to wood components swelling and/or shrinking corresponding with periods of higher and/or lower temperatures and humidities. Packaging systems incorporating plastic and cardboard were shown to offer some protection against humidity changes. For the Australian wood-manufacturing sector to achieve and maintain a reputation for superior high-performance products in overseas markets, designers and manufacturers will require a clear understanding of the potential effects of changing environmental conditions on their products. When the range of conditions anticipated throughout the service life of an item is combined with data for timber stability, a manufacturer can allow for movement in the design of the item. An understanding of effective packaging systems is also necessary to ensure maintenance of timber moisture content during transportation. The research highlighted the inherent risks of exporting high-value wood products to distant markets and the need for development of a user-friendly tool, which would allow manufacturers to determine appropriate design parameters such as species, dimensions, jointing systems, adhesives, coatings and packaging for export products.
-
Item
-
Item
-
ItemAgricultural and related education : past, present and future( 1998)Research funders, providers, educators and agricultural producers were surveyed to obtain their views on the future directions and needs of agricultural and related education. Information was gathered concerning the missions, challenges and likely major changes facing universities and state government agencies associated with agriculture over the next decade. An overriding focus on issues of environmental management and sustainability was evident in answers with a need for closer interaction between providers of education and research and users of knowledge, particularly agricultural producers. The need to attract high performing and motivated students to fields servicing agriculture was highlighted in the stakeholder survey as well as the literature review, and formed part of a second survey. This survey was conducted to assess the knowledge and perceptions of students' concerning agriculture and the various careers available in agricultural and environmental fields. Year 10 Victorian students from both metropolitan and non-metropolitan regions were surveyed as it was considered that they were at the stage of making first subject choices towards future career paths. A review of changes occurring in the land grant colleges of the United States and similar institutions in Scotland indicated concerns in similar areas. It was concluded that, in common with the United States, existing provision of educational services is failing to meet current expectations of producers in terms of their need for information, creation of learning environments and involvement in decision making of educational providers. It was also noted that the development of an education/research provider partnership with industry was seen as a logical outcome of current debates by some persons from each of the employment categories surveyed. The student survey showed that a greater number of non-metropolitan students had considered a career in agriculture than metropolitan students. It was also found that the most important influence on student knowledge about agricultural careers came from parents, school, and the media; that overall student knowledge of the various careers available to graduates of agricultural science was limited, and where such knowledge existed, it was biased by misconceptions of the role and activities of agricultural scientists. Furthermore students placed great importance on high paying careers, yet did not consider careers in agriculture to be high paying. It was therefore determined that more work needs to be conducted to increase the profile of the variety and activities involved in careers available in agricultural and related areas. The two surveys indicated need for change in Australian agricultural and related education, in similar directions to changes being debated in the United States and elsewhere. This was found in particular with respect to a stronger natural resource management or an environmental approach to agriculture and related education, and enhanced information exchange between industry, and agricultural education and prospective students.
-
Item