Biological farming with microbes and trace minerals

Soil microbes in the limelight
MATTHEW CAWOOD (Rural Press)
22 Feb, 2012 05:20 AM

LONG ignored by conventional farming practices, soil microbes are now in the spotlight as the key to new productivity breakthroughs for agriculture.

Biophysicist Iain Young forecasts a time when knowledge of how soil microbes work will lead to "designer soils".

Like an architect designs a house for function and energy efficiency, farmers will be able to harness microbes to design soils that deliver certain productivity outcomes, like water use efficiency or more efficient nutrient delivery.

Professor Young, Head of the University of New England's School of Environmental and Rural Science, observes that what is currently known about soil microbiology is promising enough, but vast areas of discovery remain.

"Soil is the most complex biomaterial on the planet, and it's because of that complexity that we survive," he said.

"In a handful of fertile soil there are more organisms than all the humans that have ever lived. We know, because we have counted them."

Microbe counting and identification has only recently become possible using new molecular tools, which is why around the globe, scientists are modifying the long-held view of soil as a bucket, readily topped up with a nutrient cocktail when depleted, with the understanding that soil is an ecosystem.

"When you understand soil as an ecosystem, you realise that if you alter one component of the system, it has knock-on effects," said soil microbiologist Pauline Mele.

"Ten years ago, we only knew about one per cent of the organisms in the soil. The new tools are showing us the other 99 per cent."

Associate Professor Mele, who works with the Department of Primary Industries Victoria, is co-ordinating the second soil biology project funded by the Grains Research and Development Corporation.

A recent GRDC release on the project begins: "The science of soil biology is following on the heels of minimum till farming - hailed as the next productivity revolution and a potential source of widespread gains in the cropping sector."

Prof. Mele has more scientific caution than to talk of revolutions, but she too is excited about what the field has to offer.

"Farmers are starting to question the conventions of farming, and the effects that these regimes are having on soils. Under certain practices, they are seeing soil health decline."

Soil microbiology is known to suppress crop disease - plant diseases run rampant in lifeless soils - enhance nutrient uptake, "and provide a whole range of functions that lead to better plant performance".

Prof. Mele is aware of the biological farming community, which uses microbes and nutrition to strategically enhance crop performance.

But her current aim is to assess how existing conventional farming practices affect soil microbes, and how that in turn affects production.

For instance, some high-input cropping systems may short-circuit some soil microbe communities, meaning that the farmer is paying for a service that biology might otherwise provide free under a more balanced approach.

"For example, we have a range of projects that will give us greater insight into the role of free-living nitrogen-fixing bacteria in crop nutrition."

"We already know that the amount produced will vary from between 10 and 30 kilograms per hectare per year but we don't have in-crop measures and have yet to link how stubble from previous years influences this rate."

The GRDC Soil Biology Initiative is supporting the national roll-out of a soil quality project initiated in WA (visit www.soilhealth.org.au ) which brings together tools and information for growers and advisers, including fact sheets on waterlogging, raised beds and non-wetting soils.