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South Perth, Australia

Verhoeven J.T.A.,University Utrecht | Setter T.L.,Baron Hay Court
Annals of Botany

Background Wetlands are species-rich habitats performing valuable ecosystem services such as flood protection, water quality enhancement, food chain support and carbon sequestration. Worldwide, wetlands have been drained to convert them into agricultural land or industrial and urban areas. A realistic estimate is that 50 of the world's wetlands have been lost.ScopeThis paper reviews the relationship between wetlands and agriculture with the aim to identify the successes and failures of agricultural use in different types of wetlands, with reference to short-term and long-term benefits and issues of sustainability. It also addresses a number of recent developments which will lead to pressure to reclaim and destroy natural wetlands, i.e. the continuous need for higher production to feed an increasing world population and the increasing cultivation of energy crops. Finally, attention is paid to the development of more flood-tolerant crop cultivars.ConclusionsAgriculture has been carried out in several types of (former) wetlands for millennia, with crop fields on river floodplain soils and rice fields as major examples. However, intensive agricultural use of drained/reclaimed peatlands has been shown to lead to major problems because of the oxidation and subsidence of the peat soil. This does not only lead to severe carbon dioxide emissions, but also results in low-lying land which needs to be protected against flooding. Developments in South-East Asia, where vast areas of tropical peatlands are being converted into oil palm plantations, are of great concern in this respect. Although more flood-tolerant cultivars of commercial crop species are being developed, these are certainly not suitable for cultivation in wetlands with prolonged flooding periods, but rather will survive relatively short periods of waterlogging in normally improved agricultural soils. From a sustainability perspective, reclamation of peatlands for agriculture should be strongly discouraged. The opportunities for agriculture in naturally functioning floodplains should be further investigated. The development and use of crop cultivars with an even stronger flood tolerance could form part of the sustainable use of such floodplain systems. Extensive use of wetlands without drastic reclamation measures and without fertilizer and pesticides might result in combinations of food production with other wetland services, with biodiversity remaining more or less intact. There is a need for research by agronomists and environmental scientists to optimize such solutions. Source

Hoyle F.C.,Baron Hay Court | Murphy D.V.,University of Western Australia
Plant and Soil

Aims: Despite our current understanding of plant nitrogen (N) uptake and soil N dynamics in arable systems, the supply and demand of N are infrequently matched as a result of variable seasonal and soil conditions. Consequently, inefficiencies in N utilisation often lead to constrained production and can contribute to potential environmental impacts. The aim of this study was to examine the influence of plant residue quality (C/N ratio) and extent of residue incorporation into soil on temporal changes in soil mineral N and the associated plant N uptake by wheat in the semi-arid agricultural production zone of Western Australia. Methods: Oat (Avena sativa); lupin (Lupinus angustifolius) and field pea (Pisum sativum) were incorporated into a Red-Brown Earth using varying degrees of mechanical disturbance (0 to 100% residue incorporated). Soil samples for inorganic N (NO 3 - and NH 4 +) profiles (0-50 cm), microbial biomass-C (0-50 cm) and plant N uptake were taken throughout the growing season of the subsequent wheat (Triticum aestivum) crop. Grain yield and yield components were determined at harvest. Results: Despite observed treatment effects for plant residue type and soil disturbance, fluctuations in inorganic N were more readily influenced by seasonal variability associated with wet-dry cycles. Treatment effects resulting from residue management and extent of soil disturbance were also more readily distinguished in the NO 3 - pool. The release of N from crop residues significantly increased (p = 0. 05) with greater soil-residue contact which related to the method of incorporation; the greater the extent of soil disturbance, the greater the net supply of inorganic N. Differences in microbial biomass-C were primarily associated with the type of plant residue incorporated, with higher microbial biomass generally associated with legume crops. No effect of residue incorporation method was noted for microbial biomass suggesting little effect of soil disturbance on the microbial population in this soil. Conclusions: Despite differences in the magnitude of N release, neither crop type nor incorporation method significantly altered the timing or pattern of N release. As such asynchrony of N supply was not improved through residue or soil management, or through increased microbial biomass in this semi-arid environment. N fluxes were primarily controlled by abiotic factors (e. g. climate), which in this study dominated over imposed agricultural management practices associated with residue management. © 2011 Springer Science+Business Media B.V. Source

Jacob R.H.,University of New England of Australia | D'Antuono M.F.,Baron Hay Court | Gilmour A.R.,University of Wollongong | Warner R.D.,CSIRO
Meat Science

A study was undertaken, using 2701 overwrapped loin samples aged for 5. days and subjected to a simulated retail display (SRD) for 3. days; sourced from lambs in the Cooperative Research Centre for Sheep Industry Innovation information nucleus flock, born 2007-2009. The ratio of reflectance of light in the wavelengths of 630. nm and 580. nm (oxy/met) was measured daily during the SRD, using a Hunterlab spectrophotometer. A series of linear mixed models was fitted to the oxy/met and time data to compare 4 breed types and identify relevant covariates, of 19, using a forward selection process. Breed type, pH at 24. h post slaughter and Linoleic acid concentration (LA) were the most important factors and covariates, in that order. Merino breed type, high pH and high LA reduced colour stability. Fitting a spline model to predict the time for oxy/met to reach a set value, represents an alternative to comparing oxy/met at a set time, for describing colour stability. © 2012 The Authors. Source

Golzar H.,Baron Hay Court | Burgess T.I.,Murdoch University
Australasian Plant Pathology

Canker and decline of Araucaria heterophylla (Norfolk Island pine) trees were observed during surveys conducted in the costal suburbs of Perth in 2009 and 2010. Samples from symptomatic and asymptomatic parts of trees were collected and morphological characteristics of the consistently isolated fungus analysed. The isolated fungus was identified as Neofusicoccum parvum using phylogenetic analysis of combined sequence data from the internal transcribed spacer of the rDNA (ITS), the translation elongation factor 1α, β-tubulin and RNA polymerase subunit II. N. parvum isolates were pathogenic when inoculated on excised branches of Norfolk Island pine. This species has been recorded on A. heterophylla in New Zealand, but this is the first report of this species causing decline and cankers of Norfolk Island pine in Australia and worldwide. © Australasian Plant Pathology Society Inc. 2011. Source

Seymour M.,PMB | Kirkegaard J.A.,CSIRO | Peoples M.B.,CSIRO | White P.F.,Baron Hay Court | French R.J.,Western Australian Department of Agriculture and Food
Crop and Pasture Science

Broadleaf break crops improve cereal yield through disease and weed control, increased nitrogen (N) availability and other mechanisms. In the rainfed farming systems of Australia the magnitude of the yield benefit is highly variable, yet is a major driver for adoption of break crops which are often less profitable and more risky than cereals. Declining area of break crops throughout Australia has re-ignited interest in better understanding the circumstances in which break-crop benefits can be maximised from a farming systems perspective. We compiled and analysed a database of 167 crop sequence experiments conducted throughout Western Australia in the period 19742007 to evaluate the impact on wheat (Triticum aestivum L.) grain yield from the use of narrow-leafed lupin (Lupinus angustifolius L.), field pea (Pisum sativum L.), canola (Brassica napus L.) or oats (Avena sativa L.), or following a long fallow where no crop had been sown the previous year. Adjusted for the years in which each was represented the average yield benefit to wheat compared with wheat after wheat was 0.60, 0.45, 0.40, 0.35 and 0.30t/ha following lupin, field pea, canola, oats or fallow, though direct comparisons between break crops could not be made as few experiments (3) included all species. For all break crops, the mean wheat yield increase was independent of the level of wheat yield, representing a step-change rather than a proportional improvement in yield. Analysis of the larger number and spread of lupin experiments revealed that break-crop benefits increased in higher rainfall areas, following higher yielding lupin crops (>1.5t/ha), and that the break-crop benefit in terms of yield and water-use efficiency increased significantly after 1991. These observations were often related to the level and/or effectiveness of diseases or grass weed control in the break crop; however, increased contribution of fixed N was also likely with better legume crops. For both lupin and field pea, the magnitude of the break-crop response declined as rate of N fertiliser applied to subsequent wheat crop increased, although non-N related benefits (disease and weed control) tended to dominate wheat response to lupin after 1989. Significant break-crop benefits from lupins (+0.40t/ha) persisted to a third wheat crop (n=29) but effects were inconsistent beyond that point. The magnitude, persistence and reliability of the break-crop benefits revealed in this study provide a more accurate framework to assess their likely benefit within the farming system. Further information is required to define the key 'trigger points' for the major drivers of the response water, N, weeds and disease at which the benefits outweigh the higher risk of these crops and would influence the decision to include them within the system. © 2012 CSIRO. Source

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