Solve trading barriers
From the December 2008 edition of Agriculture Today.
Potential for credits
It is well known that Australian cropping soils have low levels of soil organic matter.
Farmers are encouraged to implement practices that increase organic matter, such as stubble retention, to increase agricultural productivity and soil health.
Increasing soil organic matter increases the quantity of carbon stored in the soil, so can contribute to mitigation of climate change.
Thus there is potential for such practices to earn carbon credits.
Landholders in the US currently earn credits for management of soil carbon in cropping and grazing land in the voluntary market through the Chicago Climate Exchange.
The federal government plans to introduce national emissions trading through a Carbon Pollution Reduction Scheme in July.
However, since agriculture will be excluded at least until 2015 and since the decision on whether to include agriculture will not be made until 2013, the federal Carbon Pollution Reduction Scheme will not provide an incentive for soil carbon management, at least in the short term.
A group of NSW soil scientists is overcoming barriers to inclusion of soil carbon in emissions trading.
Impacts of management practices on carbon sequestration in soil are unclear, with some proponents claiming large potential and others dismissing the possibility.
"Detractors additionally say soil carbon is too costly to measure, and changes in soil carbon too difficult to audit," NSW Department of Primary Industries senior research scientist, Dr Annette Cowie, said.
"In preparation for potential inclusion in the national Carbon Pollution Reduction Scheme in future, and for inclusion in the voluntary carbon trading market, it is important to investigate these objections," she said.
So soil scientists from NSW Department of Primary Industries (DPI) and the Department of Environment and Climate Change are collaborating to look into each of the issues.
Dr Cowie says in the same way that carbon trading based on forestry offsets uses models to predict sequestration, soil carbon models can estimate sequestration through agricultural practices.
"To increase confidence about the potential for altered management practices to sequester soil carbon, researchers are undertaking paired-site studies, comparing the soil carbon stock between adjacent areas under different management," Dr Cowie said.
Comparisons include high and low input grazing land management; conventional crop rotations versus response cropping or inclusion of pasture phase; and revegetation of grazing land with native tree and shrub species.
A second component of the project is an examination of the potential for a novel soil amendment, biochar, to increase soil carbon.
DPI scientists have started an incubation study to investigate the turnover rate of biochar carbon, and conducted life cycle assessment of greenhouse gas mitigation through the use of biochar.
Contact Dr Annette Cowie, (02) 9872 0138, annettec@sf.nsw.gov.au
Annette Cowie is internationally recognised for her expertise in forestry and climate change. Her current research focuses in part on soil carbon dynamics and she is a co-leader of a key International Energy Agency collaborative research program examining biofuels as alternatives to fossil-based fuels.
Spectroscopy quick, accurate but too expensive for routine use
A soils project assessing implications for emissions trading is developing the capacity to use mid-infra red (MIR) spectroscopy for quick, cheap measurement of soil carbon.
This method requires accurate calibration, for which an extensive soil archive maintained by the NSW Department of Environment and Climate Change is being used.
The MIR method is being used to measure soil carbon in the paired-site studies.
"Although MIR greatly reduces the costs of measuring carbon in soil samples, it would not be economically feasible to do routinely for emissions trading," NSW DPI’s Dr Annette Cowie said.
Dr Cowie says the costs of sampling are too high, due to the great spatial and temporal variability of soil carbon that occurs naturally in the paddock.
Rather, the results of this project will be used in soil carbon models to estimate the impacts on soil carbon of changes in management practices.
Such models will enable development of emissions trading based on agricultural soil carbon management on the voluntary market, if not in the mandatory national scheme.
Further reading
Staff profile: Annette Cowie
