Vetiver Grass Hedges for Water Quality Improvement in Acid Sulfate Soils, Queensland, Australia

摘要

Acid sulfate soils are weak mechanically and therefore highly erodible, if drain banks are not properly stabilised, they are prone to collapse, dumping into the drains eroded soil and sediments, which are highly acidic and loaded with heavy metals and nutrients. Low flow velocities in the drains allow iron mono-sulphides and metal oxides to accumulate due to the high iron, aluminium and other metal concentrations in drainage waters. In north Queensland, the establishment of vetiver grass has been shown to control channel bank erosion, lower frequency of drain maintenance, trap sediments in runoff water and reduce acidic loading by exposing less acid sulfate soil in the drain wall to oxidisation and leaching. A trial was established in south Queensland to demonstrate the effectiveness of vetiver hedges in water quality improvement by stabilising highly acidic drains banks and trapping nutrients, sediment, agrochemicals and cane trash. Intensive monitoring and sampling of the section of drain planted with vetiver, a drain section without and the contributing run-off has demonstrated the economic and environmentally effectiveness of vetiver grass in improving water quality in term of Ph, trash input, sediment and dissolved oxygen etc.