Phosphorus in the form of phosphate has a crucial involvement in RNA, DNA and cellular metabolism, and all forms of life depend on it. Along with nitrogen and potassium, phosphorus is essential for healthy plant growth — and its supply through fertilizer is a mainstay of modern agriculture.

Reserves of the phosphate rock used to make such fertilizers are finite, and concerns have been raised that they are in danger of exhaustion. It has been argued, for example, that data from the US Geological Survey point to the available supplies peaking in as little as 25 years time (see Nature 461, 716–718; 2009). Because there is no substitute for phosphate in agriculture, this might present an urgent and substantial problem. But initial findings from the World Phosphate Rock Reserves and Resources study conducted this year by the IFDC, an international non-profit organization based in Muscle Shoals, Alabama, and formerly known as the International Fertilizer Development Center, suggest that phosphate rock deposits should last for between 300 and 400 years.

Accurate information about phosphate reserves is hard to come by, and the IFDC concedes that more work is needed to hone its estimates. The mining industry, governments and interested researchers should accept the organization's invitation to collaborate in this process.

The phosphate issue runs beyond gaining assurances that total global supply will meet demand. There remain important concerns that phosphate and other fertilizers are being squandered in some parts of the world, whereas farmers in other regions cannot obtain them at a reasonable cost.

After decades of wanton overuse, farmers in the United States, Europe and elsewhere are now using sophisticated assessments to tell them when, how much and in what proportion fertilizer should be applied. That has led to a flattening out in global demand for phosphate fertilizer, despite continued growth in food production.

But elsewhere in the world, especially in Asia, farmers are still applying fertilizer in excess (see Nature doi:10.1038/news.2010.498; 2010). At the same time, farmers in the poorest countries such as some in Africa, find fertilizer prices inflated to unaffordable levels by high transportation costs and local market conditions.

In addition, current fertilizer-production methods fail to maximize the efficient conversion of phosphate rock into fertilizer. The supply of the rock is heavily concentrated in two nations, China and Morocco, on whose good faith the rest of the world relies for its phosphate supplies. That faith has been shaken by extreme price fluctuations in recent years.

The need for sustainable use of fertilizers is largely missing from discussions on approaches to sustainable development.

Yet the heavy dependence of food production on fertilizers, inequalities of supply and the need for sustainable use of fertilizers — including recycling — are largely missing from discussions on approaches to sustainable development. They were only mentioned in passing, for example, at the United Nations' world summit on food security in Rome last November.

Hydrologists, soil researchers and food scientists have begun to raise awareness of some of the issues surrounding phosphates. A discussion will be devoted to the topic at the Crop World 2010 meeting in London next week, in which researchers will be joined by industry and government representatives, including John Beddington, the UK government's chief scientific adviser, who has worked hard to raise political awareness of food-security issues.

These efforts would be strengthened if an international body, such as the UN Food and Agriculture Organization, started to seriously champion the issue of sustainable fertilizer use. The organization already tracks fertilizer demand and supply, and has produced reports on phosphate fertilizer use. It doesn't have a specific programme for sustainable fertilizers, but its departments of agriculture and natural resources do some work in this area, giving it a base on which to build. It now needs to push this issue out from the sidelines and into the policy-making process that will shape the future of agriculture and sustainable development.