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Cotching W.E.,Tasmanian Institute of Agricultural Research | Kidd D.B.,Australian Department of Primary Industries and Fisheries
Agriculture, Ecosystems and Environment | Year: 2010

Soil quality information has been collected at 272 sites across Tasmania. Soil target values were developed for six key soil quality indicators, with values dependent on soil order and land use. The selected indicators were pH (H2O), organic carbon, extractable phosphorus, exchangeable sodium percent, bulk density and aggregate stability. Soil quality monitoring sites were biased to agricultural land uses, which was justified due to these land uses being more likely to result in soil degradation than conservation or native forestry. Cropping and perennial horticulture land uses had a greater proportion of sites outside targets for organic carbon and bulk density than grazing pasture and forestry. Most intensively used soils were within pH targets. Aggregate stabilities at many sites were outside targets under cropping and irrigated pasture indicating that cropping sites had an increased risk of erosion. Extractable phosphorus levels were below target for most dryland pasture sites and above target for most irrigated pasture sites. Soil order explained more variability in organic carbon, aggregate stability, bulk density and ESP than land use but land use explained more of the variability in pH and Olsen P than soil order. © 2010 Elsevier B.V. All rights reserved. Source

Lisson S.N.,CSIRO | Cotching W.E.,CSIRO | Cotching W.E.,Tasmanian Institute of Agricultural Research
Agricultural Systems | Year: 2011

A combination of high input management systems, high annual rainfall and deep, permeable soils in northern Tasmania create conditions that are conducive to high drainage and nitrogen losses below the root zone. An understanding of the extent and mechanism of such losses will enable farm managers and their consultants to identify and implement more sustainable management practices that minimise potential adverse financial and environmental consequences. Analysing the fate of water and nutrients in farming systems is complex and influenced by a wide range of factors including management, soil characteristics, seasonal climate variability and management history of the paddock/farm in question. This paper describes a novel farm system modelling approach based on the model APSIM, for analysing the fate of nitrogen and water in mixed vegetable-based farming enterprises. The study was based on seven case farms across the Panatana catchment in northern Tasmania. Substantial simulated drainage losses (>100 mm average seasonal loss) were apparent for all crop and rotation elements across all farms in response to the surplus between crop water supply and crop water use. Crop nitrogen demand was found to be close to crop nitrogen supply for all crop and pasture rotation elements with the exception of potato, which had an average surplus nitrogen supply of 89 kg. N/ha. This resulted in potato having much higher nitrate nitrogen leaching losses (32 kg. N/ha) compared to other crops (<10 kg. N/ha). Simulations suggest that practicable management options such as deficit-based irrigation and reduced N fertiliser rates will maintain current levels of productivity while reducing potential offsite N loss and generating significant financial savings via reduced input costs. © 2011. Source

Forrester D.I.,University of Melbourne | Forrester D.I.,Cooperative Research Center for Greenhouse Gas Technologies | Collopy J.J.,University of Melbourne | Beadle C.L.,Cooperative Research Center for Greenhouse Gas Technologies | And 4 more authors.
Forest Ecology and Management | Year: 2013

Thinning, pruning and fertiliser application are used by forest managers to increase growth rates of retained trees and to improve log quality. Understanding whether growth responses are due to changes in light interception, light-use efficiency (LUE) or both, and whether they are subject to treatment interactions could assist the design of more productive and light-use efficient plantations. Two levels each of thinning, pruning and nitrogen fertiliser treatments were applied in factorial design to a Eucalyptus nitens plantation in south-eastern Australia at age 3.2years, and responses measured to age 8.1years. Treatments were: unthinned, or thinned from ca. 900 to 300treesha-1; unpruned, or 50% of the live crown length pruned of the largest-diameter 300 potential sawlog crop treesha-1; and nil, or 300kgha-1 N fertiliser. Light-use efficiency was defined as annual above-ground biomass (AGB) or stem-wood growth per unit of absorbed photosynthetically active radiation (APAR). Growth responses were associated with changes in both light interception and LUE. There were interactions between thinning and pruning: thinning effects were weaker for APAR, and stronger for LUE for pruned than unpruned trees. During the first year after treatment, thinning increased AGB growth of the 200 largest-diameter sawlog crop trees (SCT200) by 34% (7.1-9.5Mgha-1year-1), APAR200 by 24% (0.77-0.95GJm-2year-1), and LUE200 by 13% (0.93-1.05gMJ-1); fertiliser application increased AGB200 growth by 23% (7.4-9.1Mgha-1year-1), APAR200 by 6% (0.83-0.89GJm-2year-1), and LUE200 by 13% (0.93-1.05gMJ-1). Thinning and fertiliser application both increased APAR200 by increasing tree leaf areas, and increases in LUE were associated with increases in photosynthesis. Pruning reduced tree leaf area by about 75%, but AGB200 growth and APAR200 were only reduced by 12% (8.8-7.7Mgha-1year-1) and 37% (1.06-0.67GJm-2year-1), respectively, and LUE200 increased by 36% (0.84-1.14gMJ-1) during the first year after treatment. Pruning increased LUE by removing the least efficient lower canopy foliage, and by increasing the efficiency of the remaining foliage. This study shows how changes in stand structure, crown architecture and tree nutrition can be used to alter APAR and LUE, and improve our understanding of responses to silvicultural interventions in eucalypt plantations managed for solid-wood products. © 2011 Elsevier B.V. Source

Acuna T.B.,University of Tasmania | Dean G.,Tasmanian Institute of Agricultural Research | Riffkin P.,DPI Victoria
Crop and Pasture Science | Year: 2011

Average wheat yields in the high-rainfall zone (HRZ) of southern Australia are predicted to be around 10tha-1, yet most regions fall short through a lack of locally adapted cultivars or abiotic stress that constrains yield. Wheat yields in Tasmania can be variable but have exceeded this potential yield in some field trials and have thus approached that of other traditionally high-yielding HRZ environments such as northern Europe. A contributing factor to high wheat yields in Tasmania is the cool-temperate climate, which tends not to have extremes in temperature (cold, heat) as may be experienced in HRZ environments elsewhere. Hence an understanding of crop growth, development and yield of wheat of locally adapted wheat cultivars in Tasmania may improve our understanding of the basis of yield formation in other HRZ in Australia. This was evaluated by conducting an analysis for adaptive response of grain yield in 10 wheat genotypes to a range of 14 environments that were favourable for wheat production or experienced constraints to growth. Crop growth and yield formation was then examined in detail for all or a subset of these genotypes in three field trials with contrasting environments, two of which included a time of sowing (TOS) treatment. Environment accounted for around 90% of the sum of squares (SS) in the multi-site analysis of yield. Six environment groups were identified using cluster analysis, two of which were clearly separated in response to frost at flowering or putative biotic stress, which constrained yield to 1.8 and 6.8tha-1, respectively. Waterlogging was also a significant abiotic stress in one of the TOS field trials. The late-flowering cultivar Tennant had the highest yield in the presence of waterlogging and by avoiding frost at flowering, although it suffered a yield penalty of 35 and 66%, respectively, compared with the average across environments. The highest-yielding genotypes averaged 8tha-1 across environments and included Alberic, the breeding line K37.18 and the new release Revenue. In the detailed experiments on crop growth and development, high grain yields of 10tha-1 in Mackellar appeared to be due to increased grains ear -1, resistance to barley yellow dwarf virus and possibly higher radiation-use efficiency, although the latter needs to be confirmed. There was little genotypeenvironment interaction for grain yield, hence wheat breeders can have a relatively high level of confidence that genetic material with high yield potential should rank consistently across Tasmanian environments. Results presented in the paper will be useful in developing management and breeding strategies to increase potential yield across the HRZ of southern Australia. © CSIRO 2011. Source

Forrester D.I.,University of Melbourne | Forrester D.I.,Cooperative Research Center for Greenhouse Gas Technologies | Collopy J.J.,University of Melbourne | Beadle C.L.,Cooperative Research Center for Greenhouse Gas Technologies | And 4 more authors.
Forest Ecology and Management | Year: 2012

Thinning, pruning and fertiliser are often applied simultaneously but interactions between these treatments are rarely examined. This may inhibit managers from making the most of these silvicultural investments. This study examined whether thinning, pruning and nitrogen fertiliser application at age 3.2years, interact with each other to influence the growth and crown architecture of Eucalyptus nitens trees to age 8.1years. Two levels of each treatment were applied in a factorial design replicated three times in a plantation near Carrajung, Victoria, Australia. Treatments included: unthinned, or thinned from ca. 900 to 300treesha -1; unpruned, or 50% of the live crown length pruned of the largest 300potential sawlog crop treesha -1; and nil, or 300kgha -1 N fertiliser. All treatments interacted, such that by age 6years the relative pruning effects were greater in thinned and fertiliser application treatments. The treatment interactions observed were consistent with ecological theory relating to the influence of resource availability on defoliation. Increases in crown size after thinning and fertiliser application were associated with increases in branch sizes and longevities. Leaf area density (m 2 leaf area per m 3 volume of a given crown section) increased with height in the crown and treatments had only a minor influence on this trend. Thinning and fertiliser also increased the ratio of leaf to wood mass, while pruning had the opposite effect, and all were independent of differences in tree size. Due to these treatment effects on biomass partitioning, treatment interactions in terms of stand above-ground biomass of the largest 200potential sawlog crop treesha -1 were not significant. Despite significant variability across treatments, stand level biomass growth across all treatments was closely related to leaf area index, with deviations occurring for about one year after thinning and pruning due to increases in the growth efficiency expressed as volume growth per unit leaf area. This study illustrates the crown plasticity with which foresters can work to achieve specific management goals relating to growth rates and log quality. It also shows that responses to thinning, pruning and fertiliser application may not be independent of each other, with both thinning and fertiliser application increasing the effects of pruning. © 2011 Elsevier B.V. Source

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