THE PUSHBACK: why does GRDC attack soil carbon?

The "Soil Carbon Sceptics" are becoming active again. Even the discredited "Australian soils are too ancient and degraded to sequester much carbon" furphy has been given another airing recently by the research director of a respected industry body. The facts: age and degree of degradation are irrelevant to carbon storage capacity.

The GRDC's Alan Umbers has warned farmers about thinking of carbon sequestration as an income source at an Agribusiness Crop Updates event in Perth in February. Mr Umbers said that there is no scientific evidence to support our view that croppers can sequenter carbon in significant amounts.

Mr Umbers is a victim of the same out-of-date AGO data that has misled governments and policymakers for a decade.The lag time between the start and completion dates of trials being between 3 and 5 years, the only data available to him is conventional cropping data. But Dr K Yin Chan, Principal Research Scientist (Soils), NSW Department of Primary Industries, (one of the world's 10 most influential researchers) believes we can recover the 25 tonnes per Ha of soil carbon lost under cultivation since 1770. He calls it the "Soil C Sequestration Potential".

Here is some more scientific research:

•The NSW DPI, DECC and CSIRO are currently evaluating an increase in soul carbon recorded on grazing and cropping land from 2% to 4% recorded on “Winona”, Gulgong, between 1995 and 2005.

• There was a 0.46% carbon difference between a paddock managed by conservation farming techniques (stubble retained/no-tillage) and a paddock heavily grazed and conventionally tilled over 10 years at Greenethorpe, NSW translated into a difference of 185 tonnes of carbon per hectare (or 675 tonnes of CO2e.)

• A CSIRO study (unpublished) in Albany WA found a significant difference in organic matter between two paddocks, one stubble-burned 3 years previous then no-tillage treatment for three years (3.35% OM), the other managed with no-tillage (5% OM).

Something many critics of soil carbon trading misunderstood is the value of what appears to be small amounts of carbon.One percent of carbon is a significant amount. It can translate into 48 tonnes of soil carbon which equates to 176 tonnes of CO2e per hectare (at Bulk Density 1.6 and 30cms depth). A 1% increase in soil carbon per hectare – at $25/tonne – in this situation would be worth $4440. Multiply by a thousand hectares and you have a significant figure.

Senior CSIRO soil scientist Jeff Baldock says there is today no technical barriers to a fully-functioning market in soil carbon, and that such a market could make it ‘more economic to farm for carbon than to farm for yield.’

Mr Umber's statement that “these soils will require continued inputs of organic carbon at high levels just to remain at an elevated organic carbon level...[which]... may lead to the areas involved becoming ‘uneconomic’, as the cropping and grazing systems would have to be dramatically altered to retain the levels of organic matter needed to sustain higher soil carbon levels..." is further proof that we need to educate industry commentators about the basics. All carbon sequestration is based on changed land management. Minimum or No Till, Stubble Retention, Pasture Cropping... these techniques are becoming popular among Australian croppers.

The lack of meaningful recent data leads to many mistakes: “Simple arithmetic shows that the grains industry will be a net emitter of greenhouse gasses, to the tune of approximately 700 or so kg of emissions per hectare, or 14 million tonnes over the whole Australian crop,’’ said Mr Umber. “If, under a carbon trading system carbon is valued at (say) $20 per tonne, then rather than farmers making a return from sequestering carbon, they may end up with being asked to pay around $14 per hectare, and potentially more.” Nothing is simple about Greenhouse Gasses. No figures which do take account of soil carbon realities can be relied upon.