AHDB pilot suggests soil carbon may be underestimated by a third

British farmland soils may be storing far more carbon than current accounting methods suggest, according to early findings from an AHDB-led pilot.

Initial results from the Environmental Baselining Pilot suggest that 30% or more of soil organic carbon on participating farms sits below the commonly measured 30cm depth.

AHDB said this means current soil carbon measurement methods could significantly underestimate the amount of carbon held in farmland soils.

The findings could have important implications for how farm carbon is measured, reported and valued in future environmental schemes.

The pilot is being delivered by AHDB, with support from Quality Meat Scotland and Hybu Cig Cymru – Meat Promotion Wales.

It covers 178 farms across the beef and lamb, cereals and oilseeds, dairy and pork sectors in England, Scotland and Wales.

AHDB said it represents one of the most detailed assessments of carbon held across British farmland in recent decades.

More than 53,000 soil cores have been collected from over 5,000 fields, with samples taken to depths of up to one metre where possible.

The project has also used LiDAR scanning to assess above-ground features such as trees and hedges.

Early findings from the initial 170 farms show that around 95% of estimated carbon on participating farms is held in soils, with the remainder stored in trees and hedges.

The pilot has also highlighted major variation between different soils and locations.

Across farmland analysed so far, the average soil carbon stock is around 128 tonnes per hectare.

However, some fields have recorded more than 600 tonnes per hectare.

The highest values have been found in farmland in the Cambridgeshire Fens and Somerset Levels, where deep organic peat soils showed particularly high carbon stocks.

Chris Gooderham, AHDB’s environment director, said: “We’ve now completed the data collection phase across 170 farms, and the scale of what we’ve gathered is significant.

“This gives us a much more detailed picture of carbon on farm than we’ve had before.

“It also demonstrates the value of environmental baselining on individual farms and the valuable role farmers can play in supporting and protecting our environment.”

Alongside carbon measurements, each participating farm has completed a carbon audit.

These audits estimate greenhouse gas emissions and removals through a carbon calculator and help farmers identify tailored actions for their own businesses.

The pilot is continuing to expand, with eight additional farms joining late last year through collaboration with Hybu Cig Cymru.

AHDB said this would strengthen the dataset across different farming systems.

The levy board has also established a new Scientific and Technical Advisory Group.

The group brings together independent scientific and technical expertise to guide how the baselining data is interpreted, used and communicated.

AHDB said this would help ensure the outputs are robust, evidence-based and deliver value for levy payers.

Further insights from the pilot are being shared at a series of on-farm events throughout June.

The next phase will examine how soil type, land use and management practices affect carbon levels, helping farmers and the wider industry make better decisions on environmental baselining.