Managing to enhance soil carbon

Summary

Management actions which aim to enhance soil carbon and soil organic matter content have the potential to improve soil productivity and resilience, for example improving nutrient availability for microbial activity and improving soil structural integrity which reduces soil erosion risk.

This page will help you understand:

• key management principles and practices for enhancing soil carbon
• soil organic carbon benchmarks for South Australia’s agricultural regions
• future management challenges.

Enhancing soil carbon

DEW has worked closely with the Department of Primary Industries and Regions (PIRSA) to develop soil carbon factsheets that provide additional information about the connections between soil organic matter and soil function, and how land management can influence soil function. These can be viewed using the links below:

• Organic matter and soil functions (factsheet)
• Effects of management actions on soil function (factsheet)

To build soil organic carbon, the supply of organic matter inputs, particularly legumes (through plant leaf and root residues and root exudates), must be greater than the loss of organic matter through microbial decomposition, leaching and erosion. Soil nutrients, particularly nitrogen, must also be in sufficient supply to aid sequestration of stable soil organic matter via microbial decomposition.

Management practices to enhance soil carbon include:

• minimising soil disturbance (e.g. implementing no or low-tillage), as increased aeration of soils can enhance carbon decomposition by microbes
• maximising ground cover (e.g. use of perennial production systems or cover crops), which maximise root activity and carbon inputs, supporting microbial activity and carbon sequestration -the use of deep-rooted crops (e.g. perennials) is important for storing carbon deeper in the soil profile
• ensuring sufficient soil nutrient supply (particularly nitrogen) to aid sequestration of stable soil organic matter via microbial decomposition
• increasing the clay content of sandy soils may increase the amount of carbon that could be held within the soil - this can be achieved through soil modification techniques such as clay spreading and delving, or the use of composts, manures or biochar inputs.

 Soil organic carbon benchmarks for SA agricultural districts

Soils are an important carbon sink, however, there is a limit to the amount of organic matter and carbon that they are able to realistically hold onto, based on their mineralogy and annual rainfall.

Soil organic carbon benchmarks were determined for common topsoil textures within different annual rainfall zones, which serve as guidelines to help farmers and advisors assess their capacity to increase the carbon content of their soils. The guides are based on the analysis and interpretation of over 35,000 soil samples measured by the Walkley Black laboratory method. Benchmarks are provided for each of the agricultural districts below.

Future challenges

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.

Find out more:

• Carbon sequestration from soils
• Soil modification
• Existing stock of soil carbon (map) - DEW/ASRIS
• Soil carbon forward plan for SA (report) - Sweeney et al. 2021
• Offsetting greenhouse gas emissions through increasing soil organic carbon in SA clay-modified soils: knowledge gap analysis (report) - Schapel et al. 2018
• Soil carbon in SA - SA agricultural benchmark analysis 1990-2007 (report) - Schapel et al. 2021
• Managing soil organic matter: a practical guide (report) - GRDC
• National soil strategy (report) - DAFF

Page Updated: April 2026