Rangelands NRM Blog, News & Resources

Trials measure carbon in soil and plants

A Carbon farming expert presented recent field sampling results at a Rangelands NRM-hosted field day at Yalleen Station and Millstream National Park Visitor Centre (former homestead) on 13 November 2012.

Dr Peter Russell from the Department of Agriculture and Food Western Australia, gave a presentation about the recent intensive sampling program in the Brockman land system of Yalleen Station, 200km south- west of Karratha, that was funded by Rangelands NRM.

The sampling of both soil and plant cover was undertaken to calculate the amount of carbon that is stored in both. The project aims to provide a better understanding of sequestered carbon in the rangelands of WA.

Dr Russell’s results indicate that there is an average of less than 0.4% of organic carbon in the soil, equating to about 15 tonnes of Carbon per hectare and an average of 1.8 tonnes of Carbon per hectare in the biomass or plants (grass) in the Brockman landsystem.

“Results show there is a direct relationship between soil carbon and biomass carbon,” Dr Russell said. “And generally, the more clay there is in the soil, the greater amount of organic carbon it is able to hold.”

Dr Russell said the key is to maintain as much vegetation cover as possible in order to increase the carbon amount overall.  Greater soil carbon leads to greater quality of pastoral land, native vegetation and ultimately, increased biodiversity.

Computer models have been used to run three simulation scenarios: One – Continuous set-stocking rate; Two – Continuous at reduced stocking rate; and Three – Rotational grazing (using an 11 paddock rotation).

Preliminary results showed that over 100 years, there was a net increase in carbon in scenario three, using rotational grazing whereas scenarios one and two depleted carbon stores or remained the same, respectively.

Further surveys have been undertaken at Muggon this year, a property acquired by the Department of Environment and Conservation in 1997. The site was de-stocked in 2000 and is now a conservation reserve.

Intensive sampling was undertaken on Muggon in three of its land systems: Boulder, Sherwood and Holmwood, each comprising substantial amounts of tall shrubs and trees in addition to low shrubs. Results from this survey are being collated.

Dr Russell said this carbon work is part of a larger project to characterise land systems throughout the WA rangelands.

“We are producing GIS maps showing carbon density in soil and biomass which will be used to inform biomass measurements taken from satellites and help inform computer modelling back into the GIS system.”

The aim is to have twenty land systems characterised by the end of next year.