Fertilizer from the sea

Fertilizer from the sea

An agricultural scientist unlocks the secrets to seaweed's nourishing qualities
June 30, 2010
Prithiviraj is studying how seaweed can be used
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Prithiviraj is studying how seaweed can be used as a fertilizer to affect the growth of Arabidopsis thaliana (ABOVE), a plant from the cabbage/mustard family.
Balakrishnan Prithiviraj

When the first European settlers arrived to scratch out a living on the thin soils across Atlantic Canada, they quickly made use of the seaweed on the beaches around them as a plentiful source of crop fertilizer. This age-old European practice continues in the region to this day, and now a Nova Scotia-based scientist wants to find out why.

Balakrishnan Prithiviraj, an associate professor of marine bioproducts at the Nova Scotia Agricultural College in Truro, is studying the molecular properties of common seaweed to find out how they interact with terrestrial plants. In particular, he wants to isolate the chemical compounds in seaweed that promote healthy growth in land crops.

Prithiviraj is studying how seaweed affects Arabidopsis thaliana — a small flowering plant in the cabbage and mustard family and the first plant ever to have its entire genome sequenced. In his greenhouse laboratory, he adds seaweed bio-products to the plants to see how they affect plant growth. In particular, he is interested in what happens with A. thaliana’s roots. “We are really interested in what’s going on underground,” he says. Scientists have a good understanding of what happens to plants above-ground, but root systems are still a mystery. “We’ve got a long way to go before we know for sure, but what we believe at this point is that the bio-product molecule is too big and is not getting into the plant itself but is attaching to receptors in the cell membrane.”

Prithiviraj holds a clump of brown seaweed,
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Prithiviraj holds a clump of brown seaweed, Ascophyllum nodosum, in a plant-growth room at the Nova Scotia Agricultural College.
Balakrishnan Prithiviraj

As Prithiviraj predicted, terrestrial plants treated with seaweed compounds grow faster than control plants. “There is some kind of response that triggers the plants to synthesize their own growth regulators,” he says. The plants also become more resistant to salinity, diseases, drought and insects when carrageenan — a large, flexible molecule in red seaweed — is applied. But, most surprisingly, in a test conducted on spinach by one of his graduate students, one compound from the seaweed Ascophyllum nodosum actually increased its nutritional value. “The antioxidant contents were higher in the leaves after we added the compound,” he says, “and the flavonoids in the spinach increased by between 15 and 50 percent.”

This summer, Prithiviraj and his team of graduate students are testing sample plants from a number of locations around the United States — high-value crop plants such as strawberries, lettuce, broccoli and fruit trees — to see how seaweed compounds interact with the plants. The results could have a significant impact on agriculture in places like China, India and Australia, where climate change, drought stress and salinity are major issues. And whether the crop is cotton grown in Turkey, grapes cultivated in California, apples in Taiwan or tomatoes in Italy, the global demand for cheaper and better fertilizers is high.

Prithiviraj’s work is partly supported by Acadian Seaplants Limited, a Nova Scotia-based company that sells powdered seaweed fertilizer in 65 countries around the world. But Prithiviraj says his is the first seaweed research of its kind to be conducted in Canada. Countries such as Ireland and France, on the other hand, are doing extensive seaweed research. “It’s a puzzle to me,” he says. “This region has the highest tides in the world and lots of seaweed, and yet very little has been done here to study it. The next big thing to change our lives will come from the ocean. Canada is surrounded by huge coastlines, and we have a big responsibility to explore the oceans around us.”

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