This page outlines our methodology and analytical options for our sampling service that provides a robust approach to measuring baseline carbon stock and monitoring carbon stock over time.
Measuring the changes in carbon stock in agricultural soils is increasingly important as we aim to understand the impact of farming systems on climate change. Land is our greatest potential resource for the removal of CO2 from the atmosphere and storing carbon. There is a responsibility on land managers to maintain carbon stocks and increase the removals of carbon dioxide from the atmosphere through sequestration. Management practices in arable and livestock systems can have a positive effect on the removal of CO2 but we need to be able to quantify changes in carbon stock to be able to communicate the benefits. Creating an accurate baseline measurement for soil organic carbon is essential if stock changes are to be measured in the future.
Increases in carbon stock in soils present opportunities for generating additional revenue in the future either through publicly funded support schemes such as the Environmental Land Management Scheme or, through privately funded activities that look to trade carbon credits through voluntary carbon markets (VCM).
Methodology: Understanding Soil Variables – the basis for Carbon Sampling
Understanding the levels of variability in the physical aspects of the soil is critical to allow increased accuracy and precision of sample measurements.
Electromagnetic Conductivity Scanning Survey
Our non-invasive electromagnetic (EM) scanning service collects high-density data at multiple depths through the soil profile. We use this data to then infer the degree of variability in the physical/textural characteristics of the soil within the field. This data provides valuable insights to inform other management decisions and precision agriculture operations such as variable rate seed applications.
Targeted sampling – Dividing the field into areas with similar soil properties to determine carbon stocks within field ‘zones’ as this can reduce uncertainty and aid management. We advocate that the ‘point sampling’ methodology is used as opposed to the ‘W sampling’ approach as fixed plots are more statistically accurate in measuring changes in carbon stock.
For measurement of carbon, a minimum of 30cm is required. Intergovernmental Panel on Climate Change (IPCC) guidelines require minimum of 30 cm and if deeper samples are taken, these should be sampled separately. About 40 – 50% of SOC (to 1m) is found in the top 30cm, meaning there is a considerable C stock lower in the profile. Larger changes in carbon stock occur in the upper layer but longer-term stabilization of SOC occurs in deeper soil layers and is likely to develop over longer periods.
For an initial baseline survey, we can also sample the profile from 30cm to 60cm . The benefits of this are that it will provide a more accurate measurement of carbon through the profile and gives a reference point for future measurement. Although carbon (organic matter in particular) tends to be more concentrated in the top 30 cm, cropping root systems can penetrate to 1m and beyond, having an impact on SOC as a result. The accumulation of carbon in this layer is likely to be slower and as such testing could be conducted at longer intervals (10 years plus) to measure carbon stock change.