Risk assessment of phosphorus loss from sugarcane soils — A tool to promote improved management of P fertiliser

Current strategies for phosphorus (P) fertiliser management in the Australian sugar industry do not account for the differences between different soils in their ability to sorb and release P. However, the off-site export of P from land under sugarcane has been shown to be a major factor contributing to elevated concentrations of P in stream waters draining catchments dominated by sugarcane production. This paper presents the results of a study conducted in the lower part of the catchment of the Herbert River, north Queensland, a major sugarcane growing region. Our approach was to combine a knowledge of P sorption by soil and riverine sediments with an assessment of the risk of P loss from lower Herbert sugarcane soils and knowledge of the requirements of sugarcane for P. The results provide a basis for future P fertiliser management by canegrowers which accounts for both production and environmental imperatives. They also point to an urgent need for experimentation, based on rundown of soil P fertility, to determine critical soil test values in soils of varying P sorption, and provide a useful regional framework for the design of such experimentation.