Phosphorus Fertility Assessment of Intensively Farmed Areas of Catchments Draining to the Great Barrier Reef World Heritage Area; 2: Potential of Soils to Release Soluble Phosphorus

Abstract

The potential of fertilized cropping soils (sugarcane, vegetables, fruit trees) in river catchments that drain to the Great Barrier Reef World Heritage Area in northeastern Australia to release soluble phosphorus (P) was assessed using soil chemical tests on typical soils (0–10 cm) collected in 2003. Tests included total P, diagnostic soil P tests, estimates of P buffering, and soluble and redox sensitive soil P. Routine soil P tests proved poor predictors of CaCl₂ P (0.005 M). Values≥0.20 for the Mehlich‐3 P saturation ratio separated (P<0.01) lower from higher concentrations of CaCl₂ P. The ratio of Mehlich‐3 Fe to [Mehlich‐3 Fe+Mehlich‐3 Al] is offered as a possible simple index of redox sensitive P. Part 1 (Rayment and Bloesch 2006) describes the soil survey in more detail.

Keywords:

• Horticulture
• Mehlich‐3
• P‐buffering
• redox P
• reef
• soil tests
• sugarcane

Acknowledgments

Funding from the Queensland Department of Natural Resources, Mines and Water (NRMW), Indooroopilly, and the former CRC Sugar is acknowledged. We also acknowledge the soil sampling performed by officers in other organizations. Colleagues Dave Lyons and Phil Moody of NRMW were also involved in the wider study, and Dave Lyons in particular with helped the laboratory assessment of universal extractants.