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CSIRO today issued technical guidelines on how to use tree plantations to clean up sewage effluent. Effluent Irrigated Plantations: Design and Management was launched by the Mayor of Wagga Wagga Alderman Peter Dale.
The guidelines are based on research begun in 1991 at the CSIRO Wagga Effluent Plantation Project at Flushing Meadows near Wagga Wagga, NSW.
Project Leader Brian Myers of CSIRO's Division of Forestry said "Many local government authorities are now looking to grow plantations with sewage effluent to keep nutrients out of the rivers - many have already started. Matching water and nutrient supply to plantation demand is necessary otherwise rivers and groundwater may become polluted.
'The guidelines spell out the critical issues. The aims are to maximise tree growth, to minimise the risk of contaminating ground or surface waters with nutrients and to minimise harmful changes to soil such as salt accumulation' he said.
Mr Myers said that trees' demand for water and nutrients rises until maximum leaf area for the site is reached at 2-4 years. The demand for nutrients then decreases as they are recycled through the plantation. Leaves and twigs are broken down in the litter layer - the trees reabsorb the nutrients released. Water use by the trees varies enormously from summer to winter. Storage facilities are necessary to stockpile unused sewage effluent in winter, for summer use.
At Flushing Meadows treated sewage effluent has been applied to the plantations for four years. Growth of the trees has been excellent, with some eucalypts reaching a height of 19 metres.
The Flushing Meadows experiment has involved scientists from the Divisions of Forestry and Soils, and is sponsored by the Land and Water Research R&D Corporation, Murray Darling Basin Commission, NSW Department of Land and Water Conservation, Wagga Wagga City Council and Tahara Pastoral Pty Ltd.
More information from:
Brian Myers
Effluent Irrigated Plantations: Design and Management is available from:
for $15.
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