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Wheat yields will be slashed as phosphate runs out, warns scientist

By Caroline Scott-Thomas , 21-Nov-2008

Research for the EU’s Quality Low Input Food Programme has warned that wheat yields could be more than halved by the end of the century at the latest, as the world’s phosphate supplies run out.

Phosphorus, made from phosphate rock almost entirely sourced in North Africa, is a major component in industrial fertiliser and is also used in organic farming.

It is expected that as it becomes scarcer, its price will skyrocket, impacting on grain prices in turn. It has already increased by over 500 per cent in the past two years, and rising input costs have already had dramatic consequences for food prices in recent months.

Food manufacturers could face additional pressure as they are increasingly called into question over the sustainability of their ingredients.

The research estimates that without phosphorus, non-organic wheat yields could fall from an average of eight to just 2.5 tonnes per hectare, while organic yields would not go unscathed. Even so, organic yields without added phosphate would be only marginally lower than their current level of six tonnes a hectare.

Professor Carlo Leifert, one of the scientists at the University of Newcastle working on the project, told BakeryandSnacks.com: “If you look at textbooks from 30 years ago, they estimate that we had about 500 years of phosphorus left. Now we are using about 125 million tonnes each year. Even optimists – and we are optimists – estimate that there is no more than about 60 years of phosphorus left now. And you can’t substitute one mineral fertiliser with another.”

The problem for non-organic farming is that phosphorus is needed to get optimum performance from nitrogen and potassium-based fertilisers.

Soil Association’s policy director Peter Melchett said: “Organic farming does not have this same crucial relationship.”

Human sewage as fertiliser

Both Leifert and The Soil Association are agreed that phosphate depletion could – and should – force the EU to rethink its policy which forbids the use of phosphorus-rich human sewage in organic farming but on this point Leifert is not so optimistic.

“Politicians don’t think in long enough cycles,” he said. “I think it will be 55 years before politicians do anything.”

Melchett told BakeryandSnacks.com: “In organic farming we get some potassium and phosphorus from animal manure but we would have to use human sewage to close the nutrient cycle. The EU should change the rules to allow human sewage as it does for non-organic.”

So far, the EU has ruled out the use of human sewage for organic crops – although it is allowed in non-organic farming – because of the risk of non-organic contaminants.

“Huge strides have been taken by the water industry to remove heavy metals, which have been the problem historically,” said Melchett. “That contamination has been largely resolved.”

Leifert agrees: “It is just common sense,” he said. “When you haven’t got enough manure any more you need to use human sewage. The stuff that we as humans eat is not recycled so all that phosphorus is wasted. If we want to become sustainable we need to incorporate it into our fertilisation regimes.”

It is estimated that there are between four and eight billion tonnes of phosphate left.

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