Many farm practices can help turn soil from being a carbon source to a carbon sink, to reduce greenhouse gases.

Farming practices that are effective in increasing soil organic matter (SOM) are also effective in improving crop and pasture yields.

Many farming practices in the past, such as fallowing, cultivation, stubble burning and overgrazing, have increased carbon output and sped up the decomposition of soil organic matter, particularly where native vegetation has been cleared for cropping.

All organic compounds are based on carbon, and as such can decompose to provide a food source for a diverse range of micro organisms and other soil fauna and flora.

These organisms can release many important plant nutrients, compounds that help maintain soil structure, and buffers that reduce the impact of toxins in the process.

SOM is an important part of healthy soil that we all should be trying to increase as part of our farming systems.

Soil organic matter refers to everything in or on the soil that is of biological origin, whether living or non-living.

There is a continuous need to be adding organic matter to the system to balance decomposition losses and this will maintain soil chemical, physical and biological fertility.

Soil fertility depends on factors like climate, vegetation and soil type but the amount of soil organic matter is critical to the stability of the system.

Decomposition of SOM releases nitrogen, phosphorus and many other nutrients by the process of mineralisation.

Soil particles are held together as stable aggregates by long chain compounds produced by bacteria and fungi.

This improves the soil structure and contributes to water holding capacity and infiltration, root growth and ease of cultivation.

Increasing organic matter inputs by conservation farming such as no-till systems, retaining stubbles and plant residues, use of double or companion cropping, using improved cultivars and fertiliser, has a benefit in higher yields and contributes to a sustainable system.

Addition of organic amendments like animal manures and recycled organics (sewage sludge and composts) contributes to the soil organic matter and also contains plant nutrients that can reduce our dependence on artificial fertilisers.

The pasture phase is an integral part of the farming system as well and will help to increase the SOM.

In addition to long-term trials that have been conducted at Wagga Wagga, NSW Department of Primary Industries is highlighting the importance of SOM by running a new research project that will compare soil carbon levels in a range of pasture and cropping management systems, in the hope of developing a model to predict soil carbon sequestration.