Project Background:

Phosphorus (P) is one of the most important nutrients for crop establishment, root development, and overall productivity in broadacre farming systems. However, in many regions of Western Australia and other southern Australian grain-growing areas, a significant proportion of applied phosphorus becomes chemically tied up in the soil and unavailable to plants. This process, commonly referred to as phosphorus fixation, reduces fertiliser efficiency and can limit crop performance despite ongoing fertiliser applications.

Different soil types present different phosphorus fixation challenges. On the east coast of Australia and around the Esperance region, highly calcareous soils can strongly bind phosphorus through calcium-related reactions, reducing nutrient availability to crops. In the Facey Group region and surrounding areas, forest gravels and highly weathered soils can also immobilise phosphorus due to high levels of iron and aluminium compounds. These contrasting soil chemistries create a complex challenge for growers attempting to optimise phosphorus nutrition while maintaining profitability.

With fertiliser costs continuing to rise and seasonal conditions becoming increasingly variable, improving phosphorus use efficiency has become a major priority for growers and industry. There is currently limited locally relevant information on how different phosphorus sources, placement strategies, soil amendments, and biological approaches perform across these high P-fixing soil types.

Project Summary:

The High Phosphorus Fixing Soils project aims to investigate practical and economically viable strategies to improve phosphorus availability and crop uptake across several challenging soil types in southern Australian farming systems.

The project focuses on:

• Calcareous soils commonly found on the east coast and around the Esperance region
• Forest gravel soils and highly weathered soils within the Facey Group region and surrounding areas.

Through a series of field trials, the project will test multiple rates of granular and liquid phosphorus fertilisers applied both at seeding and post-seeding. The project will also investigate the residual impact of these phosphorus applications over a three-year period to better understand longer-term phosphorus availability and crop response in high P-fixing soils.

The Facey Group trial site will be located in Williams, with the trial commencing in 2026 using canola as the first crop in the rotation.