Research to increase soil carbon storage

Research by The University of Western Australia (UWA), in collaboration with the Department of Agriculture and Food WA (DAFWA) and grower groups, has found that many surface soils in Western Australia are already storing as much carbon as they can. However, there is the potential for the lower layers to store more carbon - particularly if management practices change.

Professor Daniel Murphy said it “isn’t the end of the line for soil carbon storage … [as] there is potential for soils between 10 and 30 cm below ground to store more carbon under certain conditions” - theoretically twice as much, in fact.

Professor Murphy said researchers need to investigate management practices that could increase the amount of carbon stored at these depths. An increase in storage may offset greenhouse gas emissions and can also improve soil fertility and plant growth.

In the fact sheet ‘Organic Carbon Storage in Western Australian Soils’, Professor Murphy and colleagues refer to the Soil Carbon Research Program (2009-2012). The program measured soil organic carbon at more than 1000 sites within the Western Australian agricultural region, covering a range of agricultural practices, land use histories and soil types. The sampling sites were dominated by deep sands and shallow duplex soils, which have low surface clay content resulting in low soil organic carbon stocks.

Carbon storage ranged from 3.4 t C/ha in a Tenosol (deep sand) under mixed farming to 231.3 t C/ha in a Tenosol (deep sand) under perennial pasture. The 0-10 cm soil layer contained more than 50% of the measured organic carbon within the top 30 cm of the soil and was largely saturated. But the lower layers were at less than half their storage capacity.

A new UWA research project will assess the potential of existing and emerging management practices to increase carbon storage at these depths. The researchers hail from UWA, DAFWA, CSIRO in Adelaide and La Trobe University in Melbourne.

Research team leader Associate Professor Deirdre Gleeson said the aim of the project is “to provide farmers with options to overcome constraints to carbon storage in WA agricultural soils”. Such options to be investigated include “claying, liming or one-off soil inversion using mouldboard ploughing and spading”, she said.

The project has received funding from the Australian Government’s Carbon Farming Futures - Filling the Research Gap Program.