Rewarding British farmers for focusing on the quality and structure of their soil could help the UK tackle flooding, meet its ambitious climate commitments, and ensure sustainable food production, according to a new report by the Royal Society.
The Soil structure and its benefits report brings together the latest evidence on the diverse and under-appreciated functions our soils can perform.
As well as enabling 95% of human food production, soils filter our water, store carbon and provide habitats for an array of life. Despite this, they have too often been “out of sight, out of mind” when it comes to land management.
This looks set to change with the Agriculture Bill, the UK successor to the EU’s Common Agricultural Policy (CAP), which introduces provisions for farmers in England to access financial assistance “for protecting or improving soil quality”.
The Royal Society report highlights evidence for a number of “win-win” strategies where, by improving soil structure, land managers can increase its agricultural productivity and simultaneously deliver important societal priorities, like reducing flood risks and promoting biodiversity.
“We should be as appalled by badly managed soils in our fields as we are by the loss of our woods or wetlands,” said Professor Alastair Fitter FRS, emeritus Professor of Ecology at the University of York and a lead Fellow on the report.
“Our soils lock away more carbon than the vegetation on them, they provide 95 per cent of our food, and when managed well they limit the risk of flooding, while supporting a vast array of life. Too often, though, they are ‘out of sight, out of mind’.
“The Government is at a critical moment in setting the course for British farming outside the EU and this evidence synthesis shows how important it is that soils take centre stage in land management policy.”
The Royal Society report looks at four areas where well-structured soils – those porous enough to allow water drainage, free movement of air, and penetration by roots – have the biggest benefits.
Climate change mitigation - Huge amounts of carbon from plants and other organic matter is trapped and stored in soils. As well as helping improve soil drainage, this organic matter also makes soils more productive.
Clean water and flood prevention - Soils act as ‘natural flood management infrastructure’. Poorly managed, compacted soils don’t allow drainage, increasing surface runoff and watercourse pollution. Whereas well managed soil can slow the flow of water off agricultural land.
Agricultural productivity - Well-structured soils typically provide higher crop yields, particularly for cereal grains. This could be down to several factors, including reduced soil erosion or increased activity by earthworms and soil organisms.
Biodiversity - Soil provides habitat for an array of species that perform valuable functions, from decomposing dead matter, to controlling pests and diseases. Several species, such as earthworms, play a vital role in promoting good soil structure.
Many farmers and landowners already manage their soils to a high standard, but this has costs - and provides wider societal and environmental benefits - which current incentive schemes do not support.
Planting cover crops, rather than leaving fields bare over winter, and careful use of machinery to avoid compaction, for example, both help limit surface runoff that can contribute to flooding and soil erosion. Careful soil management also helps lock away carbon and leads to higher crop yields, but imposes costs on land managers.
The Department for Environment, Food and Rural Affairs (Defra) estimates that topsoil erosion alone costs England and Wales £150m a year – around £40m of this is attributable to productivity losses.
As the bulk of the costs from soil erosion occur off-site, affecting neighbours, downstream water users and other ecosystems, failing to factor this in can make it economically viable for land managers to exploit their soils until they degrade, while others pay the costs.
Managing soils to reflect these wider system benefits would ensure that farmers can continue to produce food sustainably, and even increase their yields, while delivering more societal goods.
Achieving this means a “shift in mindset” about how the agricultural landscape should look. We need to move away from single uses, and embrace hedges and marginal trees, short-term grass leys and the development of small wetlands, alongside crops or pasture.
The wide variety in the UK’s soils, and the ways they are used, means there is no single approach that ensures well-structured soil. A menu of evidence-based interventions will be required so that land managers can pick the method which suits the particular context.
The report concludes with four example policy scenarios, setting out the benefits and the trade-offs that they might entail. These range from a “low cost, voluntary participation scheme” with farmers self-assessing soil health, through to more scientifically rigorous systems, with regular monitoring of farmed soils. Technology will be important too: drones or lidar can be used to assess soil health and GPS-guided machinery can limit soil compaction.
Any system is likely to require significantly more support and training for farmers and regional authorities to fully understand and benefit from different management options and incentives, as well as to interpret measures of good soil structure.
Read more about the Royal Society's Living Landscapes programme.