EXPERT ADVICE ON SOIL CARBON

Soils experts claim soils can hold vastly more carbon than vegetation. A hectare of pasture can hold more that a hectare of "forest".

"1% ORGANIC CARBON in top 10cm of soil at a bulk density of 1.5 = 15 tonnes of C/ha."*

Every 1 tonne/ha increase in soil organic carbon represents 3.67 tonnes of CO2 sequestered from the atmosphere and removed from the greenhouse gas equation.**

Therefore a hectare of pasture can 'sequester' more than 55 tonnes of Carbon for every 1% increase.

"Soils tested for soils workshops with farmers at Mudgee and Rylstone have between 0.9% and 7% Carbon."***

TABLE 1. Changes in the stock of soil carbon (tC/ha) for each 1% change in measured organic carbon (OC) status for a range of soil bulk densities and measurement depths. Numbers in brackets represent tCO2 equivalent.


"If the CO2 equivalent in the above example was worth $15/t, the value of sequestered soil carbon in ‘carbon credits’ would be $1,056/ha. If the soil carbon concentration was increased by 1% to a depth of 30cm rather than to 20 cm, this would represent 132 t/ha sequestered CO2 at a value of $1,980/ha.

"If organic carbon concentrations were increased by 2% to a depth of 30 cm in the same example, this would represent $3,960/ha, that is, almost $400,000 in ‘carbon credits’ per 100 ha of regenerated land.

"These levels of increase in soil carbon are achievable, and have already been achieved, by landholders practicing regenerative cropping and grazing practices."

"This is not difficult with regenerative regimes in which new topsoil is being formed."

*Central West Catchment Management Authority, Soils paper, Farming Systems Program, January 2006

**Christine Jones, PhD. Founder, ‘Carbon For Life Inc.’ www.amazingcarbon.com Christine Jones is a grassland ecologist. She has a PhD in Agronomy/Botany from the University of New England and over 30 years’ research experience in the plant sciences. Christine’s articles, including ‘Why the Recharge-Discharge Model is Fundamentally Flawed’, ‘Grazing Management for Healthy Soils’, ‘Cropping Native Pasture and Conserving Biodiversity’ and ‘Building New Topsoil’ have received widespread publicity in print media including The Australian, The LAND, The Australian Farm Journal, Stipa Native Grasses Newsletter, Australian Salinity Action Newsletter, Holistic ManagemenT, Newsletter, In Practice, New Horizons, Agribusiness Chain, Grassland Matters, Grass Clippings, Landchat, The Australian LANDCARE magazine and GRDC GroundCover.

***Central West Catchment Management Authority, Soils paper, Farming Systems Program, January 2006

****Soil bulk density (g/cm3) is the dry weight (g) of one cubic centimetre (cm3) of soil. The higher the bulk density the more compact the soil. Generally, soils of low bulk density are well structured and have ‘more space than stuff’. The lower the bulk density the more room for air and water and the better the conditions for soil life and nutrient cycling. Bulk density usually increases with soil depth. To simplify the table it was assumed that soil bulk density did not change with depth

*****CO2 equivalent. Every tonne of carbon lost from soil adds 3.67 tonnes of carbon dioxide (CO2) gas to the atmosphere. Conversely, every 1 t/ha increase in soil organic carbon represents 3.67 tonnes of CO2 sequestered from the atmosphere and removed from the greenhouse gas equation.