Soil Carbon Roadshow Swept the Region

Back in March, NACC NRM hosted a Soil Carbon Roadshow!

The series kicked off in Northampton, where we partnered with the Northern Agri Group. This event was followed by a Legume workshop partnering with Elders and Yuna Farm Improvement Group (YFIG) to discuss the benefits of summer-sown legumes to maintain ground cover and soil moisture, build soil carbon and boost drought resilience. 

The series moved Southwards through to Mingenew, where we partnered with the Mingenew Irwin Group (MIG), then through to Dalwallinu, where we partnered up with the Liebe Group before the final day in Dandaragan, hosted in partnership with the West Midlands Group. 

Leading the roadshow were two fabulous soil scientists with a vast array of knowledge and experience. Emeritus Professor Lynn Abbott and Professor Fran Hoyle. Both of these highly acclaimed scientists are based at the University of Western Australia and relish the chance to speak with farmers and others with the power to affect real on-ground change.

Though the attendees at each event made sure to delve into Fran and Lynn’s knowledge banks extensively, and each session was different, there were some standout consistent messages. Both Lyn and Fran emphasised the importance of taking a holistic view of soils, particularly concerning soil management and functions. They also emphasised that we need to be aware that biological processes can be slow, but they are vitally important for healthy functioning soil. Building and retaining soil carbon is complex.

If you are undertaking soil tests or adding ameliorants, understand what you are testing, why you are testing, and what you want to do with that information once you have it. 

There is growing appreciation for the importance of soil biology and its impact on soil organic carbon. Where previous research has focused on the chemical and physical properties of soil, there has been a recent shift to include the biological component of soil into research. This is important in considering the potential of soils to suppress diseases naturally, improve water quality, build drought resilience, increase carbon sequestration, and reduce greenhouse gas emissions.

When discussing soil carbon, we talk in terms of fractions of carbon:

  • Labile carbon– very available and cycles quickly (i.e. over a year or less)
  • Humus– Carbon that is stable for 20 – 40 years
  • Resistant Organic carbon (this is 26 – 40% of the carbon in our soils)- this is very stable carbon, inorganic- 500 – 1000 years. 

Modelling often indicates that the top 10cm of soil is full/at potential in terms of soil organic carbon content, but the 10-20cm and 20-30cm layer is not full. The capacity of soil to retain organic matter is typically defined by texture (soil type), climate, and to a lesser extent, management. Heavier soils will generally hold more organic matter and low rainfall paired with high temperatures reduce the potential of the soil to store carbon, which makes it much more challenging to build soil carbon in hotter and drier environments.

Microbes in the soil will be limited in their functionality when the soil pH is lower than 5.5. If you can raise soil pH to 5.5 or above, you will help maximise microbial carbon use efficiency.

If you consider stubble management in terms of the carbon cycle, burning will create long term stable carbon, while decomposition will leave labile carbon in the system. These two different management options influence the soil biology differently. Where stubble is retained and left to decompose, there will be much greater nutrient cycling, and therefore ecosystem function and ecosystem services, as well as a reduced risk of erosion compared with burning. 

Our top tips for managing soil organic carbon on your property include:

  • Target degraded paddocks
  • Choose deep rooting species where viable
  • Increase water use efficiency
  • Deliver organic inputs to depth
  • Increase proportion of year (or area) with actively growing plants where viable
  • Protect your topsoil

Ultimately we want to get all the components of soil fertility working well together to build and sustain soil carbon. The best way to manage soil that is really degraded is to grow plants in it!

And a list of great resources that are freely accessible:

For some good information on biological inputs visit https://grdc.com.au/resources-and-publications/grdc-update-papers/tab-content/grdc-update-papers/2017/02/understanding-biological-farming-inputs 

For some excellent and easy to understand information:

Bugs & Biology Grower Group – check them out, Farmers interested in soil biology https://www.bugsandbiology.org/ 

A warm thank you goes out to the Liebe Group, the Mingenew Irwin Group, the Northern Agri Group, the West Midlands Group and the Yuna Farm Improvement Group for their support and assistance to bring these events to the region. 

Widespread rain across the Northern Agricultural Region put farmers under the pump with spraying and seeding preparation in full swing, and we know there were those who would have liked to attend but were unable to. If you would like some more information from the day, please contact your local grower group or contact Annabelle directly at [email protected]

Annabelle Garratt & Lizzie King – Regional Agriculture Landcare Facilitators

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