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Soil Carbon

The importance and benefits of soil carbon for soil health and CO2 sequestration is becoming a more widely discussed topic. It is especially important in organic or biological farming, but possibly has widepread implications in reducing climate change. See below for articles and reports about soil carbon.

 

Soil carbon claims: why we're staying cautious

 from Australian Organic Producer, Spring 2008, p.8.

 

The recent release of an action-oriented draft report on how Australia can tackle climate change has given carbon-storing farmers som e direction on how their efforts might be used in the future.

Australia's chief climate change advisor, Professor Ross Garnaut, has stated it's essential Australia recognises soil carbon in any long-term emissions trading scheme (ETS) which includes the agricultural sector. But he has recommended agriculture not be included in a first-round ETS, because soil carbon measurement techniques are not yet accurate enough.

Dr Brian Murphy, senior soil scientist, says there's a level of uncertainty in soil carbon levels and their measurable relationship back to farm management practices. He says obstacles to measuring soil density including cost, consistency in method and the depth of soil measured for carbon. He says once one method of measurement becomes a widely adapted the cost of its application should decrease.

Other problems with soil carbon measurement include linking the length of time carbon is intended to be captured in soil with land management techniques. 

Dr. Murphy says land management procedures could need to be agreed on  in advance for a farmer's carbon to be to be measured for offset.

"Perennial pasture, controlled livestock traffic and minimal tillage and disturbance are at the forefront of this issue - all the conservation techniques" he says. 

Comparing carbon storage to a "tap and leaky bucket", he says some climates will always be more conducive to its capture.

"The amount of biomass in soil determines how much carbon you'll store and the climate directly influences the rate and volume at which biomass will grow, and its rate of release as CO2 back into the atmosphere. 

"To put it to an analogy - biomass growing is like a tap filling up a bucket and the carbon breaking back down is a leak in the bucket. A climate where it is quite hot and soil is wet tends to have a higher rate of carbon breakdown."

He says that rather than seeking to "patch the leak" - a process affected by many variables - land managers should focus on maximising their rate of biomass production.

"If you had to describe ideal carbon storage climate it would probably be  temperate with a lot of rain - the North Coast of NSW is a good example," he says.

In terms of beneficial crops to grow he says wheat and canola are relatively low carbon nitrogen emitters, with crops like peas releasing higher nitrogen levels from harvest stubble.

And of particular relevance to drought-affected farmers, he says there are definite links between high carbon matter in soil and increased water storage capacity.

Soil Carbon Sequestration through Rangeland Management 

by W.L. Silber, V. Eviner, and D.J. Lewis

 

We will add more soil carbon articles and reports to this page as we come upon them.

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