Making Australian farms more phosphorus efficient saves money, ensures food security

Farm yields in Australia rely on phosphorus, but we could be using it more efficiently. p3anut

Phosphorus fertiliser might not spring to mind as highly important to our everyday lives in Australia, but it is critical for our grazing and cropping farms. This is because the majority of Australian soils are deficient in phosphorus, a nutrient essential for plant growth.

Phosphorus fertilisers have dramatically increased farm yields in southern Australia over the last century. In the last decade the underlying cost of phosphorus fertiliser has doubled. It is likely prices will continue to rise as the world moves to mine new phosphorus reserves that are of lower quality or harder to extract.

Phosphorus is a very important resource from a global perspective. Crop yields are limited because of the lack of available phosphorus in soils on more than 30% of the world’s arable land.

The world’s phosphorus reserves underpin global food security. The need to use these resources efficiently and equitably is clear. The world’s population is projected to reach nine billion by 2050, and there will be increasing competition for land and fertiliser resources between crops and biofuel production.

Will we run out of phosphorus?

In 2009, Dr Dana Cordell, from University of Technology, Sydney, and her collaborators estimated that “peak phosphorus” (the point where global demand for phosphorus would exceed phosphorus supply) might occur within 25 to 30 years. This is a grim prospect given global population projections. Some of the world’s poorest farmers are working in areas where food production isn’t enough to meet to current needs (e.g. in Africa), and those farmers are already struggling to afford phosphorous fertilisers.

The prediction of peak phosphorus prompted renewed research into more efficient use of phosphorus, and reviews of the global supply situation. The size of global phosphorus reserves was revised upwards and it is now considered unlikely that peak phosphorus will occur in the foreseeable future.

Nevertheless, there is a heightened awareness of the importance of phosphorus for global food security and the need for more sustainable use of this finite resource.

How much phosphorus does Australia need?

In Australia phosphorus fertiliser is an affordable way for farmers to increase crop and pasture yields and use farmland and water more effectively.

Australia uses 480 kilotonnes (kt) of phosphorus each year. The majority of it, 450kt, is used in agriculture with an average efficiency rate of 25%.

This means four units of fertiliser are applied to soil to produce one unit of phosphorus in products. Those products are exported or consumed domestically. The remaining 75% (the other three units) accumulates in agricultural soils, with a small proportion also lost to waterways.

Some phosphorus is already recycled from waste streams for re-use in agriculture. Global phosphorus shortages would increase the need to recover and recycle phosphorus from waste. For some countries, recovery and recycling alone would go close to covering their phosphorus needs.

How can we make it go further? CSIRO