A word from the RALF (September 2021)
The hype has been out there on reducing atmospheric carbon dioxide (CO₂), filling media channels across the planet for a few decades now. It’s no secret that agriculture, particularly intensive, has been targeted as one of the contributing offenders to increasing CO₂ and reducing atmospheric carbon (C). It’s the sequestering of carbon in soil organic carbon (SOC) that is viewed as a means to mitigate the impacts of increased carbon dioxide.
Dr Susan Orgill, southern leader of Soil Research and Development with the NSW Department of Primary Industries, is a leading knowledge broker in the SOC field and notes that effective management of pastures provides an important opportunity to sequester C in agricultural soils.
SOC is stored in soil organic matter, which is the organic part of soil and is made up of decomposed plant and animal materials and microbial organisms. Soil organic matter does not include undecomposed and fresh plant materials, for example, straw, mulch or leaf litter on the soil surface.
Sequestration C rate is measured in tonnes per hectare. Credits are paid per tonne per hectare per year (always consult an expert in this field for guidance).
A paper was presented to the 2021 NSW Grasslands Conference by two of the nation’s leading soil scientists, Dr Susan Orgill and Brian Murphy, retired Soil Scientist from NSW Office of Environment and Heritage. The paper was titled “Opportunities to build soil organic carbon in a challenging environment: Climate change and shifting paradigms”. Dr Orgill and Brian Murphy presented a science-based positive approach to increasing productivity and SOC levels together.
Key factors in sequestering soil carbon:
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- Grazing management is a key driver for maintaining adequate ground cover, which protects the thin skin of soil with the highest SOC levels
- Potential lies in unlocking additional farm income by selling sequestered Australian soil carbon credits which will, ultimately, contribute to improved agricultural and environmental outcomes
- While the rate of C sequestration varies due to starting SOC levels, soil and land management, soil type and climate, evidence clearly supports a rate of change typically between 0.3 to 1.0 t/C/ha/ per year (0-30 cm) for well managed pastures
- Other ways to sequester C can be through crop rotations, nutrient application (eg superphosphate), inclusion of pasture phases (eg grasses with fibrous root systems and legumes with high nitrogen content) in cropping rotations, erosion control and conservation farming practices
- Soil organic matter can be lost through intensive soil cultivation practices
- By increasing the production of biomass, replacing soil nutrients and reducing soil loss (erosion) or degradation (eg via cultivation), levels of SOC have been partially restored.
Australia is on the front foot being the only country – yes, that’s right, the only country – to deliver Paris Agreement-compliant soil carbon credits. To get the know-how and who on carbon farming and trading you will have to attend the National Carbon Farming CONFERENCE & EXPO in Albury from 23-26 May 2022.
The 2021 Soil Carbon Method is open for public consultation. Please take time to study this and contribute if you can (details here).
Hungry for more soil carbon knowledge?
Readings that provided information to this news piece are as follows:
Alan Richardson, Elizabeth Coonan, Clive Kirkby and Susan Orgill (2019). Soil organic matter and carbon sequestration. In (Eds J Pratley and J Kirkegaard) Australian agriculture in 2020: From conservation to automation, pp 255-271 (Agronomy Australia and Charles Sturt University: Wagga Wagga). Available online here.
KY Chan, A Oates, DL Liu, GD Li, R Prangnell, G Poile and MK Conyers (2010). A farmers guide to increasing soil organic carbon under pastures. Industry & Investment NSW, Wagga Wagga NSW. Available online here.
Mark Griggs (2021). Science based positive approach to carbon sequestration. Article from The Land 26 July 2021. Available online here.
