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  • From: "Tradingpost" <tradingpost@gilanet.com>
  • To: livingontheland@lists.ibiblio.org
  • Subject: [Livingontheland] Sewage waters a tenth of world's irrigated crops
  • Date: Sun, 26 Sep 2004 14:52:08 -0600


Sewage waters a tenth of world's irrigated crops
12:01 18 August 04 NewScientist.com news service
http://www.newscientist.com/news/news.jsp?id=ns99996297

A tenth of the world’s irrigated crops - everything from lettuce and tomatoes
to mangoes and coconuts - are watered by sewage. And much of that sewage is
raw and untreated, gushing direct from sewer pipes into fields at the fringes
of the developing world’s great megacities, reveals the first global survey
of the hidden practice of waste-water irrigation.

And, however much consumers may squirm, farmers like it that way. Because the
stinking, lumpy and pathogen-rich sewage is rich in nitrates and phosphates
that fertilise crops free of charge, suggests the survey presented at the
Stockholm Water Symposium on Tuesday.

“Wastewater irrigation is in an institutional no-man’s land,” said Chris
Scott of the Sri Lanka-based International Water Management Institute,
co-editor of the study. “Water, health and agriculture ministries in many
countries outlaw the practice, but refuse to recognise that it is widespread.”

He estimates that 20 million hectares of the world’s farms are irrigated with
sewage. A quarter of Pakistan’s vegetables, including salad crops, are grown
in sewage effluent, the study found.

And business is booming. One farmer in the heart of an un-named West African
city grows 12 crops of lettuce a year from his sewage farm. In many
fast-growing megacities, clean water is in desperately short supply, where
sewage is plentiful. And the sewage pipes keep flowing even in the dry
season, when irrigation canals often dry up.


Toxic waste

Farms hooked up to sewage pipes make big profits. The study found that in
parts of Pakistan the price of fields watered by sewage pipes is twice that
of neighbouring fields irrigated with clean water.

In Mexico, Jordan, Israel and Tunisia, sewage is specially treated to remove
pathogens and make it safe for irrigation. But in India, China and Pakistan,
the study found that treatment is rare. The sewage is added to fields
complete with disease-causing pathogens and toxic waste from industry.

Sewage is probably the biggest source of water for urban farming, which
provides an estimated one fifth of the world’s food, said Scott. In
Hyderabad, the Indian city where he works, “pretty much a 100 per cent of the
crops grown around the city rely on sewage,” he said. “There is no other
water available.”

Many consumers would not buy produce at markets if they knew it had been
grown in sewage, he agrees. “Often farmers take the produce to distant
markets, where customers don’t know how it is produced.” And farmers
themselves run the greatest risks of disease, he points out.

But the study concludes that banning the practice is not usually practicable.
“We need to recognise that sewage is a valuable resource that grows huge
amounts of food. So instead we should help the millions of farmers involved
to do it better,” said Scott.




  • [Livingontheland] Sewage waters a tenth of world's irrigated crops, Tradingpost, 09/26/2004

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