What is Soil Carbon?
CarbonLink
CarbonLink is focusing on the role of soil in absorbing carbon from the atmosphere to offset our emissions and reduce our carbon footprint MoreSoil carbon sequestration is a function of appropriately managed agricultural plants acting as a ‘carbon pump’ to increase the carbon levels of agricultural soils. Traditional grazing and cropping practices have at best a neutral effect on soil carbon. New management methods such as cell grazing and pasture cropping actually increase the soil organic carbon (SOC) as a result on their focus on root development and production.
Soil scientists around the world have recognised the ability to ‘build new soils’ and increase SOC under intensive management systems. Dr Christine Jones talks of the importance of SOC and the fact that healthy grasslands can contain more than 100 times the amount of carbon in the soil than in the vegetation above the soil surface.
Plants, via photosynthesis, take carbon dioxide from the atmosphere and when combined with water, sunlight and chlorophyll convert the different compounds into carbohydrates, oxygen and water. A large proportion of the carbohydrates (where the carbon ends up) make up the root system of the plants. The remaining bulk ends up either still standing as part of the grass sward, eaten by animals (and then recycled via dung) or knocked down onto the soil surface to create litter and ground cover. The rotational nature of these grazing systems causes the root hairs to slough off after each graze and be replaced during the regrowth process, effectively ‘pumping’ carbon into the soil each time the roots are sloughed off.
With proper management of soil organic matter (SOM) the SOC, which is 58% of SOM, can easily be maintained and locked up in the soil. SOC falls into three categories. These are:
It can be seen that up to 90% of SOC is stable for decades to thousands of years. Additionally, the deeper the carbon is sequestered, the more stable it is and perennial grass roots can go to depths of 10m.
Soil carbon sequestration is an ideal method of combating the GHG levels in the atmosphere for the following reasons:
Soil scientists around the world have recognised the ability to ‘build new soils’ and increase SOC under intensive management systems. Dr Christine Jones talks of the importance of SOC and the fact that healthy grasslands can contain more than 100 times the amount of carbon in the soil than in the vegetation above the soil surface.
Plants, via photosynthesis, take carbon dioxide from the atmosphere and when combined with water, sunlight and chlorophyll convert the different compounds into carbohydrates, oxygen and water. A large proportion of the carbohydrates (where the carbon ends up) make up the root system of the plants. The remaining bulk ends up either still standing as part of the grass sward, eaten by animals (and then recycled via dung) or knocked down onto the soil surface to create litter and ground cover. The rotational nature of these grazing systems causes the root hairs to slough off after each graze and be replaced during the regrowth process, effectively ‘pumping’ carbon into the soil each time the roots are sloughed off.
With proper management of soil organic matter (SOM) the SOC, which is 58% of SOM, can easily be maintained and locked up in the soil. SOC falls into three categories. These are:
| Pool | Turnover Rate | % of SOC |
| ACTIVE | Monthly to years. (Includes microbial biomass and labile organic compounds) | >5% |
| INTERMEDIATE OR SLOW | Decades | 20-35% |
| RECALCITRANT OR CHARCOAL | Hundreds to thousands of years. | 60-70% |
It can be seen that up to 90% of SOC is stable for decades to thousands of years. Additionally, the deeper the carbon is sequestered, the more stable it is and perennial grass roots can go to depths of 10m.
Soil carbon sequestration is an ideal method of combating the GHG levels in the atmosphere for the following reasons:
- Unlike increasing efficiency and using alternative power sources, soil carbon sequestration actually removes carbon from the atmosphere and locks it up for decades to thousands of years.
- It is a safe agricultural practice that has been used for more than 17 years in Australia. Cell grazing and pasture cropping work with nature and look create a natural balance in the ecosystem. Chemical and fertiliser inputs are not needed and biodiversity of plants and animals is a necessary facet for the health of the region.
- External factors such as fires, pests or droughts can be managed to ensure that carbon levels do not reduce as opposed to the lack of security of carbon in forestry plantations.
- Soils hold twice as much carbon as the atmosphere and three times as much carbon as vegetation making it the largest carbon sink over which we have any control.
