Soil organic carbon is used to determine the amount of organic matter in soils and is an indicator of soil health. A long term decline in soil organic carbon has a negative impact on fertility, productivity, resilience and mitigation of climate change.
The amount of organic carbon is a balance between inputs (from plants and micro-organisms) and losses (from natural breakdown and erosion). Rainfall and soil texture are two key factors that determine the amount of carbon that can be grown and stored in soils. The various components of organic carbon have varying degrees of resistance to breakdown and the relative proportions of these can be used as an indicator of soil health. There is little data currently available and research is continuing to improve sampling techniques, analytical methods, and relationships with management practices, soil health and productivity.
The department has been in a partnership with CSIRO to assess the influence of soil type, rainfall and farming system on the amount and nature of soil organic carbon. Increasing the clay content of sandy soils, through techniques such as clay spreading and delving, has the potential to dramatically improve the amount of carbon held in the soil. The department is also working with industry groups to gain a better understanding of how soil carbon can be improved to offset carbon dioxide emissions.
Further research is required to fill significant knowledge gaps, provide a better understanding of the soils that have the greatest potential for carbon improvement, and establish the likely impact of a drying climate on long term soil carbon levels.
See also soil carbon monitoring.