An Institute of Technology Tallaght research team has patented a new kind of fertiliser, one based on nitrogen-fixing bacteria found in the soil, writes Dick Ahlstrom.
IMAGINE BEING ABLE to capture agricultural fertiliser from the air, a fertiliser that will not pollute and one that is completely natural. A Dublin-based research team managed to produce such a fertiliser and have used it successfully in the lab.
A research team from the Institute of Technology Tallaght developed the new biological fertiliser and took a patent out on it in May. Their new "N2-Fix Biotic Fertiliser" is based on the use of free-living nitrogen-fixing soil bacteria, explains team leader and lecturer in biology, Dr Gerard Colleran.
"It was an undergraduate project and was part of a suite of undergraduate projects," explains microbiologist Dr Colleran. "The student undertook to come up with an alternative to chemical fertilisers."
Third year BSc candidate Suzanne Cummins took up the challenge with Dr Colleran and the two have developed a highly promising new way to deliver the nitrogen needed to help plants grow, but without heavy doses of nitrate chemicals. It is based on the use of bacteria that exist naturally in the environment.
"There are a lot of nitrogen-fixing bacteria in the soil but they are always associated with plants like clover," he says. Clover, beans and related plants have established a symbiosis involving nitrogen-fixing bacteria that thrive on the roots of these plants in exchange for nitrate salts fixed directly from the air.
The two went in search of free-living nitrogen-fixers in the soil and found a promising candidate. They cultured this species, developed a way to deliver it to the plants and they showed that the free-living organisms can also deliver nitrates to plants.
The project is hugely important given the strictures on chemical nitrate use imposed by the EU's Nitrates Directive, Dr Colleran says. Ireland uses about 1.4 million tonnes of nitrates every year, costing up to €560 million. Nitrate use is rising, but it will have to fall over time because of the Directive, Dr Colleran adds.
He and Suzanne Cummins isolated the soil bacteria they had identified and grew large numbers of the bacteria in liquid. This was then centrifuged to concentrate the bacterial numbers. The organisms were next suspended in the standard laboratory culture medium, agar, and this in turn was dropped into sterile cold vegetable oil.
This process causes the runny agar to solidify into tiny spheres, each one packed with the nitrogen-fixing bacteria. "We produced these beads of agar through that simple process," says Dr Colleran. They also added a small amount of iron. "It keeps the oxygen level very low in the beads," he explains.
The beads were applied to window boxes of plants and their plant growth tests showed that the bacteria once back in the soil readily produced nitrate salts from the air to the benefit of the plants, but without the symbiosis seen in clover and bean plants.
"It demonstrated to us that the principle works, that a bacteria encased in an agar bead can deliver nitrogen to the plant," Dr Colleran states.
One key point is that the bacterial species they use is a spore-forming bacteria, he says. "A spore-former is a very durable and a hardy type of organism that can survive drought, can survive freezing and survive pesticides."
If conditions go bad it can go dormant to survive in the soil. "It enters a static state until better conditions arise."
He decided to enter their discovery in the annual Enterprise Ireland Student Awards, joining up with IT Tallaght business lecturer Dr Philip McGovern and business students Desmond O'Connor and Catherine Maher. The team took a third prize for their efforts.
"In the course of that competition a patent lawyer took a look at it. We realised there was potential for a commercial product and we filed a patent," Dr Colleran says.
He is now working on a "proof of concept" but much research remains to be done to prove that the bacteria can be bulked up and then applied like a standard fertiliser product.
They must discover what happens to the bacteria when applied to soils and how long it will persist there. This involves measuring changes in the bacterial population, information that will inform them about reapplication of the agar beads and their cargo of bacteria. They also need an assessment about any environmental impacts, both to the soil but also to other organisms in it - from worms to insects and other bacteria.
If successful, the approach could reduce nitrate use and its run-off into water courses and might also support efforts to develop organic agriculture - these are naturally occurring bacteria already in the soil.