There is money to be made in carbon farming but claiming carbon credits is only the icing on the cake for landholders.
Soil organic carbon (SOC) is the largest component of soil organic matter, and results in higher moisture-holding capacity and increased ability to hold nutrients through an increased cation exchange capacity.
Certain types of soil organic matter can hold up to 20 times their weight in water. For every 1 per cent increase in soil organic carbon, in absolute terms, the available water holding capacity of the soil is increased by 16.8 litres (almost two buckets) of extra plant available water per square metre in the top 30 centimetres of soil with a bulk density of 1.4 grams per cubic centimetre. This equates to 168,000 litres of water that could be stored per hectare, in addition to the water-holding capacity of the soil itself.
Major soil disturbance results in the loss of soil organic carbon. This happens rapidly where long fallow and complete tillage practices are used. Complete ground cover with green growing plants can reverse the loss of soil organic carbon, hence the widespread interest in pasture cropping and zero, no-till and conservation farming practices. Changing grazing management to a cell, rotational or time-control grazing system is also effective.
Where to start with soil carbon
Any registered soil carbon project involves making an eligible change to your farming practices and meeting several criteria. Thomas Elder Consulting can work with you to create a plan, develop a land management strategy and facilitate the baseline testing of current soil organic carbon levels.
Greatest results are observed on properties with low carbon but high sequestration potential, such as paddocks that have been overgrazed in the past, or an area conventionally fallowed. However, even minor increases in soil carbon over time can reap significant rewards.
Once the project area is outlined, Carbon levels are measured at the beginning of a project to establish baseline carbon stocks. TEC is able to support the baseline soil sampling. Subsequent measurements are taken at the discretion of the project owner but at least every five years for the duration of the project.
Soil sampling costs
Baselining is the first critical step in any soil carbon project and involves measuring soil carbon stocks on the target land area. The initial carbon stocks are used to calculate any future soil carbon sequestration gains so, the sooner you baseline, the more soil carbon you will potentially have to trade.
The cost per hectare decreases with property size. The upfront costs mean soil carbon projects are usually suited to large landholdings, but the feasibility of a project can vary greatly depending on the soil type, climate and rainfall.
The viability of a soil carbon project on small properties will likely increase as time goes on, and it is possible to bring together aggregations of neighbouring properties.
When sampling during baselining:
- Sample more than the top 300 millimetres of soil. There is often more soil carbon below 300mm than above and this carbon can be expected to be very stable. Well-managed land is expected to promote deeper soil carbon.
- Detailed soil mapping is important because few paddocks are uniform. Many current sampling methods can only estimate the total amount of soil carbon and don’t provide any information about how soil carbon varies across paddocks and the property. Without this information, it is hard to identify the “sweet spots” or relationships between management practice and soil carbon levels.
- Soil variation is the enemy of accurate measurement of soil carbon. Accurately assessing soil variation to a depth of 1 to 1.5 metres greatly improves the accuracy of the soil carbon measurement. The more accurate the measurement, the more carbon is saleable due to lower variation in the estimated carbon yield.
Article written by TEC agricultural consultant and soil specialist, Peter Spies.