AUSTRALIA needs a uniform, cost effective testing system that accurately measures that actual amount of active carbon in soils.
Speaking at sustainable agriculture discussions at Imbil on Sunday, soil testing expert Rob Cumming said the focus on the total amount of carbon in Australia was painting an inaccurate picture about what improvements advanced farming and livestock management systems had delivered for historically low carbon content soils.
"The amount of carbon in Australian soils has decreased over time through processes including erosion, overgrazing, and mechanical farming," Mr Cumming said.
"However, conservation farming and minimum tillage systems have directly caused carbon levels to increase.
"It is the same in pastures. Carbon has been increased through advanced grazing methods, typically better rotational grazing systems that maintained ground cover."
Mr Cumming said the problem was the tests typically used to measure total carbon in soil samples were not sophisticated enough to accurately measure the difference between inactive charcoal, which could be 0.9-1.1pc of a sample, and the crucial active carbon, the 0.1 percent of the sample which "did the work" in the soil.
"There is too much analytical noise in the testing to be confident about soil tests when we are trying to determine the changes in active carbon and the make up of that active carbon," Mr Cumming said.
"Total carbon can be measured for $2.50 to $7 a sample, but we're looking at $70 or more for many multiple samples if we want to properly measure and understand the cream, the bit that really matters in our soils.
"What we need is a uniform, cost effective testing system to accurately measure the amount of active carbon."
Mr Cumming said accurate measurements would also enable land managers to credibly demonstrate that sustainable agriculture systems could and did increase soil carbon levels.
"Measurements of total carbon can make what are really major increases in active carbon look small," he said.
"We need to be able to demonstrate is we are really achieving 30-40pc gains in active carbon, which is the part of the soil that matters, where all the work is done sequestering carbon and feeding plants."
The sustainable agriculture discussions were organised by rural science graduates from the University of New England's class of 1972.
Following graduation, Mr Cumming worked in research and field work roles before spending more than 35 years in soil testing laboratories.
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