Mobilising microbes to rescue farmland

bentham-sooleThere are huge potential benefits to the agricultural sector from a Flinders University research project that will trial the use of lupin crops as a way of eliminating accumulated herbicide and pesticide residues in the soil.

Environmental health scientist Associate Professor Richard Bentham and plant physiologist Associate Professor Kathleen Soole have won a $76,000 Australian Research Council Linkage grant for a research collaboration with Injekta Pty Ltd, an Adelaide based agronomy company. Injekta will contribute $18,000 to the project.

Associate Professor Bentham said that soil contamination poses a major problem for commercial farmers, because repeated use of chemicals such as sulfonyl urea to control weeds can eventually render the soil unfit for further crop production.

He said that lupins, with their extensive root systems, have the potential to remediate polluted soil through a process known as rhizo-remediation – they enhance the action of microbes living in their root zones that break down toxic residues.

“The idea is to use lupins as a rotation crop to clean the soil up for other crops, particularly cereal crops,” he said.

Associate Professor Bentham said that the approach relies on a fortuitous chemical resemblance.

Because lupins secrete aromatic compounds – compounds that contain a benzine ring in their structure  – their presence enriches microbial populations that will then, in theory, go on to degrade the similar structures found in herbicides and pesticides.

Associate Professor Bentham said  there is also the possibility of a “double whammy” effect: “Lupins have a dense root system: not only will they clean up the soil, but they also have the potential to improve phosphorous and nitrogen availability in the soil at the same time”.

“The idea is that the soil will actually end up in a better condition, just from the natural process of growing lupins in it.”

Farms in drier climates are particularly susceptible to contamination, Associate Professor Bentham said.

“Herbicides persist much longer in drier soils because there is less microbial activity in the absence of water,” he said.

“Once you get a plant in, they provide more moisture around the roots, as well as giving additional aeration through the channeling of the root and diffusion of gases through the root surface.”

The research represents an Australian “first”. “Rhizo-remediation in Australia has been very focused on cleaning up metals – this is the first time a croppable species is being looked at to clean up organic contaminants,” Associate Professor Bentham said.

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