On poor sandy soils near Geraldton, a WA Department of Agriculture project found soil carbon accumulating at an average of 6.1 tonnes per hectare per year across several perennial grass plantings, with high end results of 11 t/ha/year.

Another recently-completed project on similar poor sandy soils looked at soil carbon stocks under annual pastures compared to native bushland, and found no difference beneath the two forms of vegetation.

The methodology that WA Agriculture Department development officer Tim Wiley and his colleagues used to come up with the perennial grass result is in dispute, holding up a paper being published on the project.

However, Mr Wiley observes that the sampling was strictly Kyoto-compliant.

"The question is, what the hell is happening?" he said.

At last year’s Carbon Farming Conference in Orange, NSW, he theorised that the whopping perennial grass result might be due to the soil life shifting from bacterial dominance under the annual plants common across WA's farming systems, to fungal-dominant perennials.

"Bacteria are just like little pigs—they eat all the organic material and burn it off as carbon dioxide," Mr Wiley said.

"Mycorrhizal fungi produce enzymes that convert the labile carbon into humus.

"We're thinking that the fungal system beneath the perennials means that we’re losing less carbon dioxide out of the soil, and that’s reflected in the carbon stocks we're measuring."

While Mr Wiley’s project missed out on a share of the $20 million in Commonwealth soil carbon research funding, he’s hopeful of a tie-in with another project that will help ground-truth the contentious sampling methodology.