Peak phosphorus: our most important nutrient running out

There are no substitutes for phosphorus in agriculture.

That's the hard truth that appears in the 2009 issue of the United States Geological Service annual commodity survey for phosphorus.

It's printed in every issue in the same place in that dry official document, but now it seems to take on a special significance - in the last few years some analysts have claimed production of phosphorus has already peaked, and demand is rising continuously. It is becoming painfully clear that we need to start seriously looking at how we manage this vital nutrient.

Life-giver

Obtaining sufficient phosphorus is crucial for the survival of all forms of life – it forms an irreplaceable part of cell membranes, energy transfer molecules and DNA – it is truly part of every living thing.

Compared to how important phosphorus is to life's flourishing, it is often the hardest nutrient for organisms to obtain in the natural world, making it a 'limiting factor' of many ecosystems, or as science-fiction writer Isaac Asimov wrote in On Chemistry, 'life's bottleneck'.

As in the wild, so on our fields - phosphorus, alongside nitrogen and potassium, is one of the three major nutrients needed for plant growth. Increasing the availability of phosphorus is a key technique used by farmers of all persuasions in order to improve their yields.

In the last 100 years, world agriculture has developed an increasing dependence on mineral phosphate fertilisers – a suite of compounds produced exclusively from  phosphate rock. Extracted from phosphate rock mined from Morocco to Florida, phosphorus has been spread on farmers' fields to the tune of 1 billion tonnes of pure phosphorus since 1950.

Until now, the main concerns about phosphorus production were how to manage the toxic and radioactive byproducts of phosphate mining and reducing what ecologists call eutrophication – the toxic growth of algae when excess phosphorus spreads from the land into watercourses. The non-renewable stocks of phosphate rock were treated as if they were limitless.

Suddenly however, it seems the limits are almost upon us. In 2007, physicist Patrick Déry applied to phosphate rock the same statistical method that has been used consistently to predict when oilfields will peak. He found that phosphate production has already peaked. If true, that would be catastrophic news, especially for the less-industrialised world, where demand is growing for phosphorus fertiliser at several percent a year, soils are generally much more deficient in phosphorus and higher fertiliser prices will be much harder to absorb.

Will it, won't it?

While Déry's analysis has its detractors, there is a growing consensus that peak phosphorus is a real threat. Just last month, the esteemed scientific journal Nature published an article entitled 'Phosphorus – the disappearing nutrient'. One conclusion of the article was that the lack of urgency in implementing solutions to phosphorus depletion could lead to catastrophe.

So how long have we got? Governments, mining companies and fertiliser companies all have incentives to guard the information they do have, meaning it is difficult to form a definitive answer. Eric Kueneman, deputy director of the Food and Agriculture Organisation's Plant Production and Protection Division admitted to Nature that the body has no real idea about the future of phosphate reserves. 'To give a reliable answer to the question, “will phosphates run out?” we need a crystal ball,' he said.
 
Some groups, made up of scientists rather than clairvoyants, are placing the date of peak phosphorus in the near future. The Global Phosphate Research Initiative, a growing group of academics concerned about phosphorus scarcity, says in its Declaration on Global Phosphorus Security: 'we are likely to see a peak in global phosphate rock production within the next few decades after which demand will exceed supply.'

The world had a preview of such a situation in 2008, when the mismatch between demand and supply caused a 700 percent increase in the price of phosphate over just a year. This triggered an international panic – China placed a 100 per cent tariff on its phosphorus exports, and rocketing fertiliser prices triggered demonstrations and a fatal stampede in India. The price of phosphate  has returned to 'only' around 3 times the 2005 level, but the spike signals how unpredictable the price of phosphorus inputs will be.

Organics to save the day?

It's clear that phosphate rock is politically sensitive, radioactive, overused and, most worryingly, becoming scarce. Dependence on mined phosphorus is one of the major flaws of conventional agriculture. So can organic agriculture save the day?

Jack Hunter of the Soil Association thinks so: 'organic farming in many ways represents mainstream farming-in-waiting. Because organic farming uses much less phosphate rock, much more effectively, it represents the best use of this depleting material'.

But it's not quite so simple. Studies in North America and England found phosphorus levels were typically low in organic farms, with the lowest levels often in the fields that had been farmed organically the longest. Nathan Nelson, an authority on nutrients in organic systems at Kansas State University, is familiar with the problem. Most organic farms, he says, are on land that once received chemical phosphorus fertilisers, and some are living off this legacy, gradually depleting the soil of phosphorus.

According to Nelson, the most problematic scenario is when farms are relying on ploughing in nitrogen-fixing cover crops to provide the main source of nutrients, as these crops reap nitrogen from the atmosphere but add no extra phosphorus. 'These [particular] organic farms are maintaining high production based on stored soil phosphorus,' he believes.

One of the products organic farmers are permitted to use to add phosphorus is far from green - crushed phosphate rock itself.

Apart from being of widely varying quality, a problem with adding this 'crude phosphate' to organic fields is the presence of heavy metals and radionuclides that remain in the unprocessed rock. The risks could be significant, but there is very little data or testing on the radioactivity or toxicity of crude phosphate. 'The risks are so clear cut and yet no one looks at it,' says researcher and organic fertiliser producer Dr Nikolas Stuttenhein.

Human waste

In contrast with crude phosphate, another, more sustainable source of phosphorus is highly regulated – human waste. One analysis shows about one sixth of the phosphorus that is mined each year ends up in our toilets, mainly as urine, and presently only 10 per cent of that is returned to our fields. Reusing such a concentrated source of phosphorus is essential, according to experts such as Carlo Leifert, who holds the Research Development Chair in Ecological Agriculture at Newcastle University. 'We need to redesign the whole waste system,' he says, 'and we have about 30 years to do it'.

As the Ecologist has pointed out, there are bureaucratic and systemic hurdles standing in the way of returning human waste to the land, even urine, which is relatively safe. While one might expect organic farmers to be leading the way, they are faced with a blanket ban on human excreta under EU organic regulations. Jack Hunter of the Soil Association says the Association follows the EU regulations, but is aware of the potential of human waste.
'We are bringing the issue up at the EU level, via IFOAM, the International Federation of Organic Agriculture Movements,' he says.

Demanding less

Broadly speaking, the challenge facing organic farmers is not so different then from the challenge the rest of the world faces – how to maintain or improve yields and soil fertility without relying on phosphate rock.

There's no silver bullet. According to Dana Cordell of the Institute for Sustainable Futures at the University of Technology, Sydney, and co-founder of the Global Phosphorus Research Initiative, the strategy should involve 'dramatically' reducing demand and recovering and reusing the phosphorus that currently is leaking from the system. The mix of ways to achieve this in naturally phosphorus-poor areas such as the tropics or Australia will look very different from that which is right for  Europe, but the toolkit includes diet changes, wiser fertiliser use and reusing human waste (see box, below).

Problematically though, high quality information and co-ordinated policy responses to the challenge of peak phosphorus are almost non-existent. In contrast to other vital agricultural inputs, such as water or nitrogen, there is no international body responsible for phosphorus resources.

'Before we start talking about detailed policy measures, we need some kind of global co-ordination to oversee these kinds of tasks,' says Cordell. Not that she is suggesting a go-slow. 'Before 2007 there wasn't much discussion at all about this issue, which is alarming, considering what we know now... I don't think we have the luxury of a lot of time.'

It seems the world needs to rapidly start managing its phosphorus - it could be the most precious element of all. 

Useful links
Phosphorus Futures website

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