Australasian Science: Australia's authority on science since 1938

It’s Time to Prepare for Peak Phosphorus

By Graeme Batten and Lindsay Campbell

A looming global shortage of an important fertiliser necessitates the development of phosphorus-efficient crops, recycling of phosphorus from sewage and even separating it from urine.

Australians should be very concerned and New Zealanders alarmed by their dependence on phosphorus. Why? On a per person assessment, Australians and New Zealanders use 5.3 and 15.4 times more phosphorus than the world average, which is 2.4 kg per person per year.

The reason for the high usage per person is the small populations of these countries relative to their production of exported products – mainly cereals from Australia and milk and meat from New Zealand. As our populations increase, more food will be consumed locally relative to the amount of food exported, but the demand for imported phosphorus fertiliser will remain high.

The food security of nations is highly dependent on phosphorus. The need for continual inputs of phosphorus fertiliser for food production cannot be taken for granted. Crop yields would immediately decline on average by an estimated 20% and by 30-40% within 5 years if phosphorus fertilisers became unavailable. This would be disastrous. The world population increases by about 75 million people annually and crop yields must increase by about 1.2% each year to keep pace.

Furthermore, the availability of phosphorus for food production cannot be taken for granted. The major reserves of the world are now concentrated in the USA and North Africa, but the latter will become the dominant provider in only 50 years from now. Supply could be limited at short notice due to economic, political or military events. Australia has small reserves of phosphorus but these should be preserved until imports become unavailable or prohibitively expensive.

Increases in fossil fuel costs will lead to increases in transportation costs, and these will flow onto the price of fertiliser at the farm gate in Australia and New Zealand. An illustration of the volatility in the cost of phosphorus occurred about 8 years ago. The price of triple superphosphate, a fertiliser containing about 19% phosphorus, rose from $207/tonne in January 2007 to more than $1100/tonne in August 2008. Within a year the price collapsed to $220 , but since then it has been increasing progressively

Both Australia and New Zealand must prepare for life with less affordable phosphorus. This scenario must be seen as a community challenge and not simply the responsibility of the agricultural sector.

Worthy goals in Australian and New Zealand should be to reduce the export and promote the recycling of phosphorus. Some studies estimate that the amounts of phosphorus exported in wheat and rice grains can be reduced by 10–15% in the short term by switching to phosphorus-efficient cultivars. The saving in fertiliser-equivalents would be some $30 million annually for the wheat industry and $750,000 annually for the rice industry – more than enough to fund a serious R&D program dedicated to reducing our dependence on imported phosphorus.

The phosphorus efficiency of every genotype in every crop-breeding program should be known. While traditional analytical methods are accurate, they are costly in terms of time, chemicals and technical skills. However the rapid, chemical-free technology of near infrared spectroscopy is able to assess phosphorus in plant and grain samples, and with little effort could be used to identify and utilise phosphorus-efficient lines in plant breeding programs.

To reduce our dependence on imported phosphorus we must change the one-way phosphorus path to a closed phosphorus cycle. This would include reducing dependence on some products, increased recycling of phosphorus in waste products such as sewage, and separating phosphorus in urine.

This is a worthy challenge for all citizens.

Graeme Batten is Honorary Professor in the Department of Plant and Food Sciences at The University of Sydney and Editor-in-Chief of the Journal of Near infrared Spectroscopy. Lindsay Campbell is a senior lecturer in the Department of Plant and Food Sciences at The University of Sydney.