Scarcity of phosphate for fertiliser worries soil experts

Scarcity of phosphate, an indispensable crop fertiliser, is worrying soil experts, given the voracious plans of Brazil and many other countries in the race for biofuel leadership.

A salt of phosphoric acid salt, phosphate is a chemical compound made up of a central phosphorous atom and four oxygen atoms.

Phosphorous is a "finite and irreplaceable" mineral, whose known reserves that are economically viable for exploitation could run out in 60 to 100 years if the current pace of global consumption continues, said Euripedes Malavolta, agronomist and researcher at the University of Sao Paulo.

"Without phosphorous there will be no agriculture, nor biofuels, nor life. Humanity will end," he said. Other minerals, like nitrogen, potassium, cobalt, magnesium and molybdenum, are also essential, but their sources are not as limited and, except for the first two, their consumption is relatively low.

"Phosphate has the risk running out before petroleum does," José Oswaldo Siqueira, professor of soil microbiology at the Federal University of Lavras, told a bio-energy conference held last month in Sao Paulo. Strong expansion of agriculture for bio-energy purposes would accelerate depletion of phosphate, which is a fact to consider in any "strategic vision" for that sector, he said.

Categorising biofuels -- ethanol and biodiesel distilled from sugarcane, maize and other crops -- as "renewable" should not blind us to the fact that some aspects of farm production, like soils and mineral nutrients, are not in infinite supply, said Siqueira, a programme director at the National Council of Scientific and Technological Development.

For example, Australia is not interested in dedicating itself to agro-energy production because of its limited water resources, he added.

Without a "hardly probable" discovery of large, new phosphate sources, the current reserves will last only until mid-century, says Jean Marc von der Weid, public policy coordinator for the non-governmental ASPTA, which provides consulting and services for alternative farming projects and defends agro-ecology.

Environmentally friendly farming techniques sharply reduce the loss of fertilisers by recovering what is left in plant waste, he said. Furthermore, priority could be placed on crop species and varieties that are more adaptable to soils poor in phosphorous.

"I am a voice calling in the desert, like John the Baptist," complains Malavolta, who for a long time was alone in Brazil in warning about the importance more efficient use of phosphate. By improving acidic soils with lime "one can use one-third of the phosphate we were utilising before," he said by way of example. And Brazil has soil that is very acidic and poor in phosphorous, he added.

Genetic modification to develop varieties that need less fertiliser is another path yet to be followed. "No magic of genetic engineering will produce a species that doesn't need phosphate," but it can produce one that consumes less, he said. The problem in Brazil is that available technologies are not being employed to make best use of fertiliser, such as soil and plant analysis, and more fertiliser than necessary is applied to crops, wasting a resource that "is impossible to make last indefinitely," Malavolta explained.

The excess of phosphate means that only 30 percent is absorbed by the plants and reduces productivity, according to Siqueira. Most of it is left in the soil. Another portion, through erosion and runoff, contaminates water supplies and leads to the proliferation of algae, which can be harmful to human health.

The absorption of 30 percent occurs in the first planting, but the following plantings can use much of the phosphate retained in the soil. But, because lack of knowledge about the problem, most farmers apply phosphate fertilisers to their crops with every year's planting, creating waste and harm, says Malavolta.

No-till planting, in which plant residue from previous harvests is left in the field, fertilising and retaining moisture, is another way to re-use phosphorous, he noted.

Recycling garbage and sewage to recuperate phosphate is another key measure to extend the reserves, agree Malavolta and Von der Weid.

Another complication Malavolta mentioned is the concentration of phosphate mines in the countries of North Africa, especially Morocco, which has 42 percent of the world's reserves, including the Western Sahara, a territory fighting for its independence.

China, with 26 percent, and the United States, with eight percent, are other leaders, but they also consume a great deal in domestic farming so do not export as much as Morocco.

If the Arab countries lose the power they hold in the world's oil markets, they will maintain it with phosphate, which will also become scarce and expensive, the expert predicts. It would not be surprising if an organisation of phosphate-exporting nations were to emerge, a la OPEC, he jokes.

Brazil, with just 0.4 percent of the world's phosphate reserves, relies on imports, mostly from the United States, Russia and Morocco.

IPS