BBC News Online: Sci/Tech

Cool salt water boosts plant growth

Scientists in Hawaii have found a way to harness cold seawater to irrigate crops.

The team, from the Common Heritage Corporation of Oahu, pump ashore cold salt water from 600 metres (2,000 feet) down in the Pacific.

But the seawater never touches the soil or the plants themselves.

Instead, the plastic pipes in which it is pumped through the soil create condensation which waters the plants. This eliminates the need for conventional irrigation.

The pipes also cool the plants' roots, which the researchers say makes them behave as they would in a perpetual spring.

Strawberries from the desert

They say non-tropical species including artichokes, brussels sprouts and roses can flourish.

Over 100 food species have been grown successfully, including strawberries, asparagus and basil.

The corporation president, Dr John Craven, describes the technique as "a breakthrough for world agriculture, which allows us to convert the desert into a sustainable habitat".

He says it creates an environment in which nutrients are pumped rapidly up the plants.

"The colder the root, the tastier the vegetables. And when you harvest, the plant doesn't die; it just keeps growing."

Japan is planning to use the technique for a commercial spinach-growing operation in Okinawa, which is expected to pay for itself.

Electric power

The Hawaiian demonstration plot is part of a site belonging to the Natural Energy Laboratory and is on a lava desert near the international aiport.

Other experiments there involve using the seawater to boost the growth of fungi, and in aquaculture.

The laboratory was set up to generate electricity from the temperature differential between warm surface seawater and much colder water from the depths.

Work on this is continuing at the laboratory, although the concept seems too expensive for practical use at the moment.

But the pipelines installed for that research are still pumping up 60,000 litres (16,000 US gallons) of water a minute at 5 degrees Celsius (42 F).

Potential for cooling

A bigger pipeline is planned, which will bring water from 900m (3,000 feet) down, and will triple the volume of water for research.

The cold water is also being used for air conditioning. The laboratory estimates the monthly saving on cooling its buildings at more than $4,000.

A similar system is at work at Cornell University in New York, using water from 80m (270 feet) down in Cayuga lake.

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Internet Links

Natural Energy Laboratory of Hawaii
Common Heritage Corporation

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