As seen in Farm Weekly, 28/03/2024

Irwin Hunter & Co. has a wide range of quality pasture seed and specialist pasture mixes, providing an excellent diversity of species as Cover Crop options aimed at improving soils and building carbon levels through sequestration, which provide an option for meeting one of the 'Carbon Farming' requirements of the ERF to earn Australian Carbon Credits Units (ACCU's).

What is the deal with carbon farming?

It is using practices that get carbon from the atmosphere and into the soil, with a portion of it preferably in a stable state.

How do we get carbon into our soils?

Photosynthesis is the basis of life on Earth.

Plants and some microbes capture light and combine it with carbon dioxide and water to create sugar and oxygen.

The plant uses these sugars to grow and releases them through its tissues to feed above- and below-ground microbes.

It is the root exudates that drive carbon farming.

When a plant is vegetative, up to 80 per cent of the carbon it captures through photosynthesis is released as an exudate, predominantly root exudates.

These root exudates feed the soil biology, creating nutrients that the plants can use.

The deeper the roots of the plant exuding exudates, typically the more stable carbon in the soil.

Most of the nutrients taken up by the plant are done through a process known as rhizophagy, where the roots absorb the microbes into the plant cells, remove the cell walls and digest the cytoplasm.

The nucleus is replicated and returned to the soil, where it reforms its cell wall and does its microbial duties before getting absorbed by the plant again.

The stable carbon is mainly derived from dead plants or organic matter and microbial processing.

The deeper in the soil, the less chance it has of oxidising and being rereleased into the atmosphere.

This is where cover crops come in

Cover crops will allow a plant to be kept in the vegetative stage for as many days as possible throughout the year, extending the days of root exudates feeding our soil biology.

An annual grain crop only releases root exudates for 30 to 40 days of its life.

Species selection of the cover crops can include some deep-rooted tap roots, extending the rooting zone into which root exudates are released.

After harvest, a warm season cover crop can be used to have something growing from November into January or later, depending on moisture and heat.

This again extends the number of days that we are feeding carbon into our soils.

Once the carbon cycle starts, soil material joins together and starts creating soil aggregates.

This allows water and air to flow through our soil, allowing the microbes to work with the plants and freeing up nutrients for plant growth.

Rain can now infiltrate the soil, increasing plant growth and microbial activity.

So, the system starts to feed on itself, capturing more carbon, creating more plant growth, and increasing microbial activity.

Mixes to consider for a cover crop

Irwin Hunter & Co's Cover Crop Plus mixes for both winter and summer and Green Manure Mix are recommended for farmers looking to do a cover crop.

Mixes such as SouWest Pasture Mix, Self Regeneration Mix, Maximix and Interow Mix have diverse components that can also be used as a cover crop.

IH Seeds also provides the additional option to suit your farm requirements with a "Mix & Match" where a blend can be designed to help address your soil constraints to help build carbon in your soils, keeping plants growing, supporting the soil biology, and sequestering carbon into the soil.

Planting cover crops can effectively improve the sustainability and productivity of Western Australian farming systems while also providing a range of environmental and economic benefits, additional forage for livestock, improving soil health, reducing erosion and providing a source of nutrients for subsequent crops.

Contributions by Kevin Elmy, author of various publications on cover cropping.

Contact your local farm supplier or Irwin Hunter & Co regarding their extensive range of pasture seed and mixes.