Variations in Soil Carbon Stocks with Texture and Previous Landuse in North-western NSW, Australia

Australia's land managers will need specific information about the best locations at which to sequester carbon if they are to take advantage of the recent Carbon Farming Initiative of the Australian Government under which carbon offsets can be created through sequestration of carbon in soil and trees. The literature indicates that soil texture and previous landuse are important determinants of soil carbon content. This paper describes the results of work to assess the current levels of soil carbon and the extent to which they vary with previous landuse and soil texture in the Namoi Catchment Management Authority in North West NSW, Australia. Soil samples were taken at 74 sites for determination of soil carbon concentration and stocks as well as soil texture and landuse in the last 10 years. There was wide variation between sites in soil carbon concentration and stocks which were greatest in those soils which had not been disturbed by cultivation and in soils with higher clay content. Thus, the greatest potential for carbon sequestration is in soils with the lowest carbon concentration, those which have been previously disturbed, and with higher clay content.

Maintaining any increased carbon concentration will depend on minimizing disturbance, increased carbon input and minimizing loss of carbon through soil erosion. As these factors all vary significantly on a regional and landscape basis it will be important for land managers to have access to information which allows them to choose the sites at which potential for sequestration of soil carbon is greatest.