‘Bespoke’ biochar: The future of beneficial soil carbon fertilisers

‘Bespoke’ biochar: The future of beneficial soil carbon fertilisers


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Wollongbar DPI soils scientist Dr Lukas van Zwieten is a world authority on the benefits of biochar as a soil enhancer.

Wollongbar DPI soils scientist Dr Lukas van Zwieten is a world authority on the benefits of biochar as a soil enhancer.

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The future of biochar as a soil amendment on Australian farms has yet to arrive, a fact that confounds Wollongbar DPI soils scientist, Dr Lukas Van Zwieten.

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THE future of biochar as a soil amendment on Australian farms has yet to arrive, a fact that confounds Wollongbar DPI soils scientist, Dr Lukas Van Zwieten, based at the department's research station on the Alstonville Plateau.

The principal researcher created and still supervises the world’s oldest scientifically replicated test plots which proves that biochar improves soil and agricultural production. 

But it seems Australian farmers, on the whole, remain under educated about this remarkable material - despite the fact that charred timber has been a part of Aussie soils since Adam was a boy.

Everytime there is a bushfire, for instance, charcoal - or biochar - is added to the soil and most farmers understand that vegetation seems to flourish where there was once a burnt windrow.

More importantly, biochar combined with specific nutrients and trace elements will create a slow release fertiliser with potentially the same cost as fossil-fuel derived chemical inputs - without acidifying soil.

Trouble is there is no where for producers to turn to find these products. The technology is still emerging and those in the know, like Dr Van Zwieten and Mark Glover from EcoWaste, say that until all the loose ends are knotted it might be best to 'wait and see'.

Meanwhile, in scientific circles, the concept of biochar as a soil soother is gaining enormous respect.

Last year Dr Van Zwieten's DPI team published 10 new papers on the subject - about the same number created during the century prior to the year 2000. 

Since then something has changed: Last year in total 1200 papers on 1200 papers on pyrolysed organic material (the charcoal or biochar is the product of pyrolysis) were published, and Dr Van Zwieten says the subject’s study has only further enhanced its respectability among academic researchers.

The next step involves the creation of ‘bespoke’ biochars that come in pellatised form that can rectify specific soil situations while improving soil carbon content, buffering against fluctuating pH and improving soil resilience.

Mr Glover envisages specific biochar fertilisers deposited in different corners of a paddock, using direct drilling and global positioning systems.

"The technology is there," he says. "But at the moment it is important not to chase brands  or vendors."

Wonderful biochar: How does it do that?

IN ground breaking studies, published last year, Dr Van Zwieten's DPI team have revealed that biochar made from softer biomass - like grass, leaves or straw - reacts with red soils to unlock phosphorous normally tied up with iron and aluminium in order to make it available to plants.

In another study, again published last year, the team revealed that biochar in the soil will increase carbon content over time.

Both studies point to biochar as a no-brainer for future farming.

When it comes to biochar, not all materials make the same end-product. 

For instance it is well known that very dense timber, like eucalypt hardwood, turns into a wonderful charcoal capable of lasting in the ground for a thousand years. 

The multitude of chambers in this crystalised aromatic hydrocarbon - with a surface area approaching 1000 square metres per gram - means microbes can live here and digest plant exudates while respiring carbon. When these microbes die they leave behind a range of plant-available nutrients. 

This home-sweet-home for microbes and nutrients helps build soil carbon and if pre-loaded with the right stuff can act as a slow release for nitrogen, phosphorous, boron, molybdenum, calcium and zinc in whatever mixture required by the farmer.

In places where existing nutrients are locked up local soils - like phosphorous - biochar can be tweaked to help make those nutrients available.

Another type of biochar is made when softer woods are pyrolyzed: Straw, leaves and grass, feedlot slurry and even human waste.

This softer biochar tends to contain more ash and can be used to react with red  soils to make phosphorus more readily available to plants. 

Normally these ferrosols lock up phosphorous in a complex relationship with iron and aluminium. Dr Van Zwieten theorises that there is an electro-molecular relationship between clay particles and conductive carbon that helps this amazing process along.

The creation of even more carbon in the soil than that added by the landholder is another intriguing dynamic of biochar.

For instance an initial addition of biochar at the rate of 10 tonnes /ha (4t pure carbon) is known to increase soil carbon content by .7 per cent over three years - from 4.5pc to 5.2pc.

But as an added bonus from nature, that application will help to increase soil carbon to 6.5pc over time, which Dr Van Zwieten says equates to an additional 13t/ha.

While biochar is a rigid structure that will last for months or centuries, depending on whether it is from hard or soft material, the added carbon from plants is more ‘labile’, meaning it is prone to movement and it won’t be all available for a crop this season; that's because it might take the form of living microbes - which have to die to release their nutrient to the soil.

But the fact remains that a biochar rich soil is more active than one without, and the result is proven to increase yield in agriculture.

Both types of biochar would likely require an extra application every few years - think of the standard hardware variety chemical respirator that uses charred coconut husk as its ‘activated carbon’; when it ‘runs out’ you can start to smell the chemical meaning that it has reached its capacity to work.

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