Water extraction by sugarcane on soils of the Ord Irrigation Area

Sugarcane is a new commercial crop in the Ord River Irrigation Area and irrigation management strategies are required for profitable production with minimal environmental consequences such as rising ground water. Knowledge of soil water properties and sugarcane water requirements is a necessary prerequisite for bestpractice irrigation. Accordingly, soil water measurements were taken to quantify the amount and depth pattern of water extraction by sugarcane on the Ivanhoe Plain in the Ord River Irrigation Area. The drained upper limit and crop lower limit of extraction were measured on 4 soil types. The amount of soil water available to the sugarcane plant varied between soil types, ranging from 226 to 167 mm in a 2.0 m profile. Sugarcane extracted water down to 1.8 m at the Central and Northern Ivanhoe sites, down to 1.6 m at the Southern Ivanhoe site, but only down to 1.0 m at the Aquitaine site. The pattern of water use over time was determined at 2 sites and showed higher crop water use before the wet season and much lower crop water use after the wet season. There was considerable reduction in the ratio of crop water use to Class A pan evaporation after the wet season. Lower irrigation frequency after the wet season on maturing crops will improve irrigation efficiency and reduce impacts on the environment. This knowledge of the different soil water properties of the 4 soil types can be used with crop growth models to develop recommendations for best-practice irrigation management of sugarcane across the Ord River Irrigation Area. These recommendations need to account for the high soil water extraction capability of sugarcane growing in this environment.