UK POLICY makers should not rely on zero or minimum tillage systems as a guaranteed way of cutting greenhouse gas emissions in their post-Brexit farming plans, a new Soil Association briefing paper has warned.

Reacting to declarations of support for min/no tillage systems from Defra Secretary of State Michael Gove, the Soil Association reminded him that he had also promised his future UK agriculture policy would have ‘as strong an evidence base as possible’.

In theory, by using minimal tillage and direct drilling, farmers minimise soil disturbance and therefore reduce erosion, with the possible added benefit that carbon is sequestered, as, over time, organic matter increases and with it soil carbon levels.

However, the Soil Association's review of the latest scientific research on conservation tillage concludes that it is not a guaranteed way of cutting farming’s greenhouse gas emissions, and the government should not treat it as such within its post-Brexit farming policy.

The briefing paper highlights recent research which found that levels of soil organic carbon can be overestimated in no/min till systems, for example when less conclusive results from deeper soils are ignored, and said: “These results support the message advocated in former studies that the no-till sequestration potential with respect to mitigating climate change is likely to be overoptimistic.”

Instead, the SA advocates a 'wider environmental approach', involving tree planting and including trees in farmland, introducing livestock onto arable farms, and longer, more diverse rotations bringing grassland into arable cropping systems, all of which are proven methods of increasing soil organic matter, and all 'typical' of organic farming systems, which should be supported by government.

The briefing paper was the last one written for the Soil Association by its long-time policy director Peter Melchett, who passed away in August. In it, he said: “Globally, agricultural soils store an estimated 9.8 billion tonnes of carbon. Managed well, they can reduce greenhouse gas emissions, but managed badly they become a source of emissions.

“There is no question that no or min till systems can produce positive results in improving soil health and soil quality, but not necessarily in reducing greenhouse gas emissions. On the other hand, despite the use of ploughing on most organic farms, organically-farmed soils have been found to have on average 21% higher levels of soil organic matter than non-organic soils.

“Conservation tillage should therefore not be relied on as a silver bullet and a much wider environmental approach using proven methods backed by strong scientific evidence, such as agroforestry and organic techniques, is needed if post-Brexit farming policy is to reduce farming emissions," concluded Mr Melchett.

More detail can be found in the full briefing at