Nutrient, Solute and Water Distribution in an Australian Native Hardwoods Plantation Irrigated with Reclaimed Water from Bolivar Sewage Treatment Works

The purpose of the Hardwood Irrigated Afforestation Trial (HIAT) is to find safe and sustainable ways to dispose of effluent water. HIAT is designed to demonstrate plantation management which is capable of using effluent waters available in a steady supply throughout the year. It aims to describe the impacts of effluent irrigation on the environment and trees. Results after three years' of plantation development show some striking differences in the way which tree species partition water use and nutrients. Preliminary water and solute balance models indicate that leaching of key nutrients and solutes is occurring in winter but that the sodic state of the soil is being maintained on an annual basis. Significant leaching of chloride and sulphate from residual soil supplies prior to irrigation has taken place. Despite leaching of several tons of calcium per hectare, an increase in the unsaturated soil has occurred with effluent irrigation. Lateral flow in the groundwater has been demonstrated which has limited the extent of mounding under the plantation to less than one meter depth in Spring.